The Office of Fair Trading said this week that it had spent approximately £3m on its inquiry into tender malpractice by contractors

In response to a freedom of information request submitted by Building, the OFT said it did not know how much it had spent on the inquiry, which last month fined 103 firms £131m for infringing competition law. It added it would be too expensive to determine the exact cost.

However, it said it could estimate the cost of the investigation as £3m, based on a proportional split of the body’s cartels and criminal enforcement division over the period of the investigation, 2004-09.

A source close to the investigation said that figure seemed “very much on the low side. It looked more like £5m-6m from where we were”.