Twenty-three partner Nottingham firm Nelsons is to swallow up its nine-partner neighbour Trumans.
Although Nelsons will now have 32 partners and 150 fee earners, it will still only be the third-largest law firm in Nottingham, behind Freeth Cartwright Hunt Dickins and Browne Jacobson.
As part of the deal, Trumans managing partner John Appleby, a prominent Law Society council member, will join Nelsons' five-partner management board.
The two senior partners at Trumans, Brian Cotton and David Close, will become consultants of the merged firm, and one partner will be leaving to pursue other interests.
Nelsons is a general practice, but is particularly well known for its criminal work. Trumans is best known for its family and private client work.
Nelsons managing partner Tim Hastings said the firm was pursuing a strategy of regional expansion and had entered into talks with Trumans in January 1998.
He said: "The merger will have the biggest impact in private client work, but it will also contribute to the other broad blocks of the practice. Those who have eyed us competitively will now have to keep an eye on us."
Colin Flanagan, chief executive at rival Freeth Cart-wright said: "This move is not particularly surprising. For a number of years, firms of 10 to 20 partners have had to meet the increasingly high expectations of their clients, and this means that firms need to have a certain critical mass."