Subsidence engineering company Clancy Consulting has pulled out of the UK Subsidence Group UKSG), citing a commercial conflict of interest.
Clancy was one of the six original members of UKSG, which provides specialist and consultancy services to the insurance industry.
The company decided to pull out because of its parallel membership with the rival subsidence engineering group, Premier Resolve.
The move makes Premier Resolve the UK's largest subsidence consultancy group, with 540 staff.
Neil Hindley, managing director of Altrincham-based Clancy Consultancy, said: "We have been members of both groups, but believe that in the longer term we are better off belonging to Premier Resolve."
Brian Clancy, non-executive chairman of UK Subsidence Group, said: "Although disappointed to be losing one of our original members, UKSG continues to go from strength to strength."
He added that since the organisation's launch in November 1999, it had secured major contracts with Axa, Northern Star and Bishopsgate.