The company, owner of agencies including Lowe and McCann Erickson, said it had uncovered errors resulting from "instances of falsified books and records, violations of laws, regulations and company policies, misappropriation of assets, and inappropriate customer charges and dealings with vendors".
Culpable employees have already been fired, or are in the process of being sacked, Interpublic said.
It said the fraud took place primarily at agencies outside the US, but did not give further specifics.
The news came yesterday, when Interpublic said it would be filing its 2004 earnings, as well as figures for the first half of 2005, by September 30. The figures for 2004 were meant to be published in March, but Interpublic was forced to push them back indefinitely after realising the extent of its accounting problems.
In a filing with the US financial regulator, Interpublic admitted that errors in its financial statements were largely the result of weak controls and its decentralised operational structure.
The errors are forcing the company to restate earnings dating back to 2000, with Interpublic saying that it expects the impact of the restatement will be material.
Along with full recognition of its accounting problems, this year has seen significant account losses for Interpublic. These include the $3.2bn (拢1.7bn) General Motors media account, which shifted to Publicis Groupe in May, and the Bank of America account, worth $600m, which moved to Omnicom Group earlier this month. Earlier this week, it lost the $315m account of DIY retailer Lowe's, also to rival Omnicom.
Michael Roth, who took over as CEO in January this year, said sorting the finances was top priority.
"I have been clear since assuming my current responsibilities that our top priority is to fix our financial controls and leave accounting issues behind us. The comprehensive review of our financial results and processes that we have undertaken is consistent with this objective," Roth said.
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