diff --git a/app/dao/services_dao.py b/app/dao/services_dao.py
index ab4e71b56..6d0b22ef8 100644
--- a/app/dao/services_dao.py
+++ b/app/dao/services_dao.py
@@ -169,16 +169,6 @@ def dao_update_service(service):
     db.session.add(service)
 
 
-@transactional
-@version_class(Service)
-def dao_remove_service_permission(service, permission):
-    for p in service.permissions:
-        if p.permission == permission:
-            service.permissions.remove(p)
-
-    db.session.add(service)
-
-
 def dao_add_user_to_service(service, user, permissions=None):
     permissions = permissions or []
     try:
diff --git a/app/models.py b/app/models.py
index ba667f599..8c1e22e79 100644
--- a/app/models.py
+++ b/app/models.py
@@ -241,7 +241,8 @@ class ServicePermission(db.Model):
     service = db.relationship("Service")
     created_at = db.Column(db.DateTime, default=datetime.datetime.utcnow, nullable=False)
 
-    service_permission_types = db.relationship(Service, backref=db.backref("permissions"))
+    service_permission_types = db.relationship(
+        Service, backref=db.backref("permissions", cascade="all, delete-orphan"))
 
     def __repr__(self):
         return '<{} has service permission: {}>'.format(self.service_id, self.permission)
diff --git a/tests/app/dao/test_services_dao.py b/tests/app/dao/test_services_dao.py
index 0c78a7940..aac063f9b 100644
--- a/tests/app/dao/test_services_dao.py
+++ b/tests/app/dao/test_services_dao.py
@@ -11,7 +11,6 @@ from app.dao.services_dao import (
     dao_create_service,
     dao_add_user_to_service,
     dao_remove_user_from_service,
-    dao_remove_service_permission as dao_services_remove_service_permission,
     dao_fetch_all_services,
     dao_fetch_service_by_id,
     dao_fetch_all_services_by_user,
@@ -46,10 +45,7 @@ from app.models import (
     InvitedUser,
     Service,
     ServicePermission,
-<<<<<<< HEAD
     ServicePermissionTypes,
-=======
->>>>>>> Updated service DAO and API end points
     BRANDING_GOVUK,
     DVLA_ORG_HM_GOVERNMENT,
     KEY_TYPE_NORMAL,
@@ -298,7 +294,7 @@ def test_remove_service_does_not_remove_service_permission_types(sample_service)
 
     services = dao_fetch_all_services()
     assert len(services) == 0
-    assert set([p.name for p in ServicePermissionTypes.query.all()]) & set(SERVICE_PERMISSION_TYPES)
+    assert set([p.name for p in ServicePermissionTypes.query.all()]) == set(SERVICE_PERMISSION_TYPES)
 
 
 def test_create_service_by_id_adding_and_removing_letter_returns_service_without_letter(service_factory):
@@ -397,7 +393,9 @@ def test_update_service_permission_creates_a_history_record_with_current_data(sa
     assert service_from_db.version == 2
     assert LETTER_TYPE in [p.permission for p in service_from_db.permissions]
 
-    dao_services_remove_service_permission(service, permission='sms')
+    permission = [p for p in service.permissions if p.permission == 'sms'][0]
+    service.permissions.remove(permission)
+    dao_update_service(service)
 
     assert Service.query.count() == 1
     assert Service.get_history_model().query.count() == 3