Oppenhoff & Rädler is undergoing a radical over-haul following its decision to merge with Linklaters.
Last week, partners at the German and UK firms voted in favour of a full merger, which will be effective from 1 January.
However, 20 per cent of Oppenhoffs' 116 partners are considering quitting the firm. It is understood they have until the end of August to decide as merger documents are due to be signed in September.
Managing partner Markus Hartung says: "There are some partners who do not share the vision and think a stand-alone strategy is the much better one.
"Some accepted the opinion of the majority and voted for merger anyway, some voted against it because they think it is the wrong direction for Oppenhoffs."
It has already been decided that Oppenhoffs' two-partner family law group will be disbanded. One Frankfurt-based partner, 60-year old GeorgBambach, will retire. The other, Max Braeuer, will concentrate on his other practice area of property.
The Berlin office is expected to be hit the hardest as the bulk of those against the merger are based there. Senior partner Peter Raue has already said he will retire.
Christoph Wagner, leading German practitioner and media and telecommunications partner, is also considering leaving. But he is one of the few lawyers facing a conflict of interest over clients and the firm is keen to retain him.
Oppenhoffs' partners have all fitted into Linklaters lockstep system. Although it has a spread of 25 points, the Germans are only able to hit the 12-point mark to take into account a difference in profits and charge-out rates.
But Hartung says that this is a transitory measure to give Oppenhoffs' partners a chance to catch up with their UK counterparts.
The firm will also embark on a recruitment drive across all practice areas and offices.