Further problems with its accounting systems surfaced last week. IPG was forced to state that its 2004 and 2005 financial reports could be late and that it might have to restate previous reports.
The news comes at a testing time for IPG. Its £1.5 billion General Motors media business is under review and it is searching for three key global media executives to run Initiative Media, Universal McCann and IPG's media assets at the holding company level.
But IPG denied the latest accounting farrago would hamper its progress.
"We do not think finding these people will be as difficult as you might imagine," an IPG source said. "The chance to build a reputation as the person who finally cracked the problem may be appealing."
However, Michael Roth, IPG's new chief executive, is nevertheless considered to have made a good start, despite having to acknowledge "material weaknesses" in the company's accounts.