The news comes after a letter to the OFT detailing TV Eye's position on agency bank guarantee levels. Agencies have now succeeded in persuading the OFT to agree their claims could be valid.
Although the OFT has not launched a formal investigation, sources say it thinks TV Eye may have a case to answer. TV Eye wants increased levels of bank guarantees, but denies it is trying to impose unfair trading practices.
The submission shows the agencies were serious when they made the OFT threat last month, which was seen by some of TV Eye's members as sabre rattling. TV Eye comprises ITV, Channel 4, Five, GMTV and Flextech's Interactive Digital Sales.
The agencies' decision to up the ante comes just weeks before a final resolution was due to be made. It means that they have effectively bought themselves time and put the onus on finding a mutually acceptable solution back on the broadcasters.
Andy Barnes, the Channel 4 sales director and chairman of TV Eye, was unavailable for comment.