The ruling is the latest blow for the OFT which has already been ordered by the Competitions Appeal Tribunal to cut fines following appeals by contractors and repay court costs.
The five latest firms to win costs back are:
Francis Construction awared £51,960.94
JH Hallam £44,857.71
Hobson & Porter £43,550.69
Robert Woodhead Ltd £48,170.78
Renew £160,000.