In one of the first clear signs that slumping credit markets are causing economic pain at law firms, Clifford Chance Monday laid off a group of associates in the structured finance area.

John Christian, the partner in charge of the London-based firm’s U.S. personnel committee, said the firm had made a difficult “business decision” to lay off the six associates in a practice group that worked exclusively for credit rating agency Standard & Poor’s. The lawyers in the group had reviewed the documentation S&P used to rate mortgage-backed securities, the market for which has collapsed in recent months.