Britain’s Competition Appeal Tribunal (CAT) reduced the 42 million pounds ($67 million) of fines imposed on the six companies, which include Kier Group, to little more than a tenth of that total.

The Office of Fair Trading (OFT) handed out fines totalling 129.5 million pounds to 103 construction firms in September 2009 for colluding when bidding for work on projects such as hospitals and schools.

The ruling put a question mark over some of processes employed by the OFT when setting fines, such as the size of the penalty it imposes in a bid to deter future infringements.

The CAT said the deterrence element of the fines — set at 0.75 percent of the construction firms’ total worldwide turnover in the last business year prior to the OFT’s ruling — was “applied mechanistically and as a substitute for an individual assessment of the relevant factors of each case.”

The OFT said it would consider the judgment in detail, alongside those in 19 other construction cases yet to be determined, and decide whether it should appeal to the Court of Appeal.

Kier, handed the biggest fine by the OFT, saw its penalty slashed from 17.9 million pounds to 1.7 million.

“Kier fully endorses competition law and, in 2007, began the implementation of a comprehensive compliance program which has been firmly embedded throughout the business,” it said in a statement.

Other firms to see their fines reduced included Ballast Nedam NV and John Sisk.

The case is not the first time the OFT has seen a lengthy investigation unravel.

Last year it cut short a long-standing investigation into price fixing in milk and butter produce, reduced the fines on those firms that accepted some liability and withdrew allegations against Britain’s top retailer, Tesco.