The OFT issued statements of objection against 112 construction firms today. Building looks at how the inquiry that led to this has developed over the past four years

2004 - OFT begins inquiry into construction industry.

27 July 2005 - The OFT says it has searched the premises of 22 Midlands firms for evidence of collusive tendering.

March 2006 - Bluestone and Mowlem become the largest companies to be raided as part of the cartels inquiry.

22 March, 2007 - The OFT announces that it has uncovered £3bn of rigged construction bids across the country and issues an appeal to companies not yet inspected to come clean in exchange for a reduced penalty.

25 May, 2007 - Kier becomes the first quoted company to reveal that it is under investigation, announcing that 20 of its tenders are being looked into as part of the OFT investigation.

30 May 2007 - Rok admits it, too, is under investigation. Galliford Try follows suit less than four hours later. The companies are followed by more quoted firms in the following days, including Balfour Beatty, Interserve and Renew.

June 2007 - Emerges that the Construction Confederation is to lead a joint representation to the OFT to appeal for leniency.

August 2007 - OFT says it is unlikely to be able to issue a list of those firms it is accusing of collusive behaviour until next year.

April 2008 - Concern emerges that public sector clients may blacklist firms involved in the inquiry. Highways Agency thought to be making inquiries over whether its firms are likely to be named, fuelling concerns that companies who are named will be dropped from tender lists.

17 April 2008 - OFT issues statement of objections against 112 firms it accuses of bid-rigging and anti competitive behaviour.

And from here…. - Firms have ten weeks to respond to allegations. The OFT will then issue fines, which could be up to 10% of turnover.