London law firms Berwin Leighton and Bircham & Co each retain a Conservative Member of Parliament as a paid consultant, according to the recently published register of MPs' interests.
Hartley Booth, MP for Finchley, is paid between £10,000 and £15,000 by Berwins, while Roy Thomason, who represents Bromsgrove, receives between £15,000 and £20,000 from Birchams.
Thomason states in the register that the arrangement with Birchams will terminate in September 1996.
A spokesman at the office of Sir Gordon Downey, Parliamentary Commissioner for Standards, said that the disclosed payments are likely to be annual contracts. The register is dated March 1996.
Neither the law firms involved, nor the MPs, were available for comment.
The register of MP's interests is designed to show how much members earn on top of their parliamentary salaries.
But MPs are required only to reveal remuneration where the work is connected to their role in the House of Commons. There is no obligation to disclose earnings where members are employed in positions which are not contingent on their job as an MP.
Consequently, a number of MPs disclose outside work but not how much they earn.
Almost inevitably, there is disagreement about whether certain jobs relate to an MP's political status.
One senior partner at a City law firm said that many solicitor-MPs acting as consultants to legal practices were former partners who did not have time to retain full-time positions.
A spokesman for the Law Society said: "There is no specific rule in solicitors' practice notes regulating the relationship between lawyers and MPs. But there is a general requirement that they don't do anything to bring the profession into disrepute."