Harrow and Barnet’s merger of legal teams could end up costing taxpayers more than it saves if errors are made, a councillor has warned.

Councillor Paul Osborn, Conservative spokesman for performance, said the merger of both councils’ lawyers to a team led by Harrow could lead to payouts if legal advisers unfamiliar with another borough’s regulations make mistakes.

It comes after a blunder in June when Barnet Council was forced to repeat a planning committee meeting when a legal officer drafted in from Harrow did not know that any decisions taken after 10.30pm in Barnet are null and void, and let the meeting continue.

The full merger begins on September 2, and the two councils believe the move will save them £4.4million a year by reducing office space and hiring fewer external lawyers.

The scheme has already been delayed since being agreed in April after difficulties agreeing the amount Barnet would pay Harrow for costs to run the department.

Cllr Osborn said: “When it comes to legal matters, if you get something wrong it can cost you hundreds of thousands of pounds very quickly.

“It’s an area that we need to be very careful in. That’s not to say we shouldn’t do it, because if you get it right sharing services can be very successful.

“But I’m not sure about our ability to manage it and it could open us up to a lot of risks.”

Under the scheme, Harrow will host the department and Barnet lawyers will become Harrow Council employees. The team will focus on their home borough’s cases to begin with, before gradually taking on work for both boroughs.

Portfolio holder for performance, Councillor Graham Henson, said yesterday that the project was “an innovative partnership” that would “reduce our back office costs and find savings that have no impact on residents”.