Gloucester City Council has announced it will be joining Tewkesbury and Cheltenham?'s joint legal service.
One Legal was set up in 2009 when the two councils merged their legal departments.
Gloucester has now confirmed it will join the partnership from 1 April in a bid to secure cost savings and become more resilient.
Tewkesbury Borough Council?s lead member for corporate governance, Cllr Jude Perez, said: '?We are really pleased to be welcoming Gloucester City Council to join our joint legal service - it's a move which will help to ensure we provide Tewkesbury Borough, Cheltenham and Gloucester with a resilient and highly skilled legal team.
'?One Legal, since it was introduced, has gone from strength to strength and we are looking forward to seeing it grow further with the addition of Gloucester City Council.?'