diff --git a/openerp/addons/base/base.sql b/openerp/addons/base/base.sql
index c0fd67ea56c..6b0812a4b40 100644
--- a/openerp/addons/base/base.sql
+++ b/openerp/addons/base/base.sql
@@ -39,7 +39,10 @@ CREATE TABLE ir_model_fields (
   required boolean default False,
   selectable boolean default False,
   translate boolean default False,
-  serialization_field_id integer references ir_model_fields on delete cascade, 
+  serialization_field_id integer references ir_model_fields on delete cascade,
+  relation_table varchar,
+  column1 varchar,
+  column2 varchar,
   primary key(id)
 );
 
diff --git a/openerp/addons/base/ir/ir_model.py b/openerp/addons/base/ir/ir_model.py
index 8fafc60c1c9..ab30836feb9 100644
--- a/openerp/addons/base/ir/ir_model.py
+++ b/openerp/addons/base/ir/ir_model.py
@@ -245,6 +245,9 @@ class ir_model_fields(osv.osv):
                                                                            "structure of the serialization field, instead "
                                                                            "of having its own database column. This cannot be "
                                                                            "changed after creation."),
+        'relation_table': fields.char("Relation Table", help="Used for custom many2many fields to define a custom relation table name"),
+        'column1': fields.char("Column 1", help="Column referring to the record in the model table"),
+        'column2': fields.char("Column 2", help="Column referring to the record in the comodel table"),
     }
     _rec_name='field_description'
     _defaults = {
@@ -287,26 +290,75 @@ class ir_model_fields(osv.osv):
         ('size_gt_zero', 'CHECK (size>=0)',_size_gt_zero_msg ),
     ]
 
+    @api.model
+    def _custom_many2many_names(self, model_name, comodel_name):
+        """ Return default names for the table and columns of a custom many2many field. """
+        rel1 = self.env[model_name]._table
+        rel2 = self.env[comodel_name]._table
+        table = 'x_%s_%s_rel' % tuple(sorted([rel1, rel2]))
+        if rel1 == rel2:
+            return (table, 'id1', 'id2')
+        else:
+            return (table, '%s_id' % rel1, '%s_id' % rel2)
+
+    @api.onchange('ttype', 'model_id', 'relation')
+    def _onchange_ttype(self):
+        if self.ttype == 'many2many' and self.model_id and self.relation:
+            names = self._custom_many2many_names(self.model_id.model, self.relation)
+            self.relation_table, self.column1, self.column2 = names
+        else:
+            self.relation_table = False
+            self.column1 = False
+            self.column2 = False
+
+    @api.onchange('relation_table')
+    def _onchange_relation_table(self):
+        if self.relation_table:
+            # check whether other fields use the same table
+            others = self.search([('ttype', '=', 'many2many'),
+                                  ('relation_table', '=', self.relation_table),
+                                  ('id', 'not in', self._origin.ids)])
+            if others:
+                for other in others:
+                    if (other.model, other.relation) == (self.relation, self.model):
+                        # other is a candidate inverse field
+                        self.column1 = other.column2
+                        self.column2 = other.column1
+                        return
+                return {'warning':{
+                    'title': _("Warning"),
+                    'message': _("The table %r if used for other, possibly incompatible fields.") % self.relation_table,
+                }}
+
     def _drop_column(self, cr, uid, ids, context=None):
+        tables_to_drop = set()
+
         for field in self.browse(cr, uid, ids, context):
             if field.name in MAGIC_COLUMNS:
                 continue
             model = self.pool[field.model]
-            cr.execute('select relkind from pg_class where relname=%s', (model._table,))
+            cr.execute('SELECT relkind FROM pg_class WHERE relname=%s', (model._table,))
             result = cr.fetchone()
-            cr.execute("SELECT column_name FROM information_schema.columns WHERE table_name ='%s' and column_name='%s'" %(model._table, field.name))
+            cr.execute("""SELECT column_name FROM information_schema.columns
+                          WHERE table_name=%s AND column_name=%s""",
+                       (model._table, field.name))
             column_name = cr.fetchone()
             if column_name and (result and result[0] == 'r'):
                 cr.execute('ALTER table "%s" DROP column "%s" cascade' % (model._table, field.name))
-            # remove m2m relation table for custom fields
-            # we consider the m2m relation is only one way as it's not possible
-            # to specify the relation table in the interface for custom fields
-            # TODO master: maybe use ir.model.relations for custom fields
             if field.state == 'manual' and field.ttype == 'many2many':
-                rel_name = model._fields[field.name].relation
-                cr.execute('DROP table "%s"' % (rel_name))
+                rel_name = field.relation_table or model._fields[field.name].relation
+                tables_to_drop.add(rel_name)
             model._pop_field(cr, uid, field.name, context=context)
 
+        if tables_to_drop:
+            # drop the relation tables that are not used by other fields
+            cr.execute("""SELECT relation_table FROM ir_model_fields
+                          WHERE relation_table IN %s AND id NOT IN %s""",
+                       (tuple(tables_to_drop), tuple(ids)))
+            tables_to_keep = set(row[0] for row in cr.fetchall())
+            for rel_name in tables_to_drop - tables_to_keep:
+                cr.execute('DROP TABLE "%s"' % rel_name)
+
         return True
 
     def unlink(self, cr, user, ids, context=None):
diff --git a/openerp/addons/base/ir/ir_model_view.xml b/openerp/addons/base/ir/ir_model_view.xml
index 4ae1dd85b34..44a44fe66bf 100644
--- a/openerp/addons/base/ir/ir_model_view.xml
+++ b/openerp/addons/base/ir/ir_model_view.xml
@@ -68,6 +68,9 @@
                                             <field name="ttype"/>
                                             <field name="relation" attrs="{'required': [('ttype','in',['many2one','one2many','many2many'])],'readonly': [('ttype','!=','one2many'), ('ttype','!=','many2one'), ('ttype','!=','many2many')]}"/>
                                             <field name="relation_field" attrs="{'required': [('ttype','=','one2many')], 'readonly': [('ttype','!=','one2many')]}"/>
+                                            <field name="relation_table" attrs="{'readonly': ['|', ('ttype', '!=', 'many2many'), ('state', '!=', 'manual')]}"/>
+                                            <field name="column1" attrs="{'readonly': ['|', ('ttype', '!=', 'many2many'), ('state', '!=', 'manual')]}"/>
+                                            <field name="column2" attrs="{'readonly': ['|', ('ttype', '!=', 'many2many'), ('state', '!=', 'manual')]}"/>
                                             <field name="selection" attrs="{'required': [('ttype','in',['selection','reference'])], 'readonly': [('ttype','not in',['selection','reference'])]}"/>
                                             <field name="size" attrs="{'required': [('ttype','in',['char','reference'])], 'readonly': [('ttype','not in',['char','reference'])]}"/>
                                             <field name="domain" attrs="{'readonly': [('relation','=','')]}"/>
@@ -171,6 +174,9 @@
                             <field name="relation" attrs="{'required': [('ttype','in', ['many2one','one2many','many2many'])],
                                                                           'readonly': [('ttype','not in', ['many2one','one2many','many2many'])]}"/>
                             <field name="relation_field" attrs="{'required': [('ttype','=','one2many')], 'readonly': [('ttype','!=','one2many')]}"/>
+                            <field name="relation_table" attrs="{'readonly': ['|', ('ttype', '!=', 'many2many'), ('state', '!=', 'manual')]}"/>
+                            <field name="column1" attrs="{'readonly': ['|', ('ttype', '!=', 'many2many'), ('state', '!=', 'manual')]}"/>
+                            <field name="column2" attrs="{'readonly': ['|', ('ttype', '!=', 'many2many'), ('state', '!=', 'manual')]}"/>
                             <field name="selection" attrs="{'required': [('ttype','in',['selection','reference'])], 'readonly': [('ttype','not in',['selection','reference'])]}"/>
                             <field name="size" attrs="{'invisible': [('ttype','not in',['char','text','reference'])]}"/>
                             <field name="domain" attrs="{'readonly': [('relation','=','')]}"/>
diff --git a/openerp/models.py b/openerp/models.py
index 12fa508341b..73fbc47aae7 100644
--- a/openerp/models.py
+++ b/openerp/models.py
@@ -391,6 +391,9 @@ class BaseModel(object):
                 'translate': bool(getattr(f, 'translate', False)),
                 'relation_field': f.type == 'one2many' and f.inverse_name or None,
                 'serialization_field_id': None,
+                'relation_table': f.type == 'many2many' and f.relation or None,
+                'column1': f.type == 'many2many' and f.column1 or None,
+                'column2': f.type == 'many2many' and f.column2 or None,
             }
             if getattr(f, 'serialization_field', None):
                 # resolve link to serialization_field if specified by name
@@ -696,11 +699,10 @@ class BaseModel(object):
                 if partial and field['relation'] not in self.pool:
                     continue
                 attrs['comodel_name'] = field['relation']
-                _rel1 = field['relation'].replace('.', '_')
-                _rel2 = field['model'].replace('.', '_')
-                attrs['relation'] = 'x_%s_%s_%s_rel' % (_rel1, _rel2, name)
-                attrs['column1'] = 'id1'
-                attrs['column2'] = 'id2'
+                rel, col1, col2 = self.env['ir.model.fields']._custom_many2many_names(field['model'], field['relation'])
+                attrs['relation'] = field['relation_table'] or rel
+                attrs['column1'] = field['column1'] or col1
+                attrs['column2'] = field['column2'] or col2
                 attrs['domain'] = eval(field['domain']) if field['domain'] else None
             self._add_field(name, Field.by_type[field['ttype']](**attrs))