The figures follow last year's client defections from IPG, whose agency networks include McCann Erickson, FCB and Lowe Worldwide.
IPG, the third- largest communications company in the world, reported a fourth-quarter operating income of £34.4 million, compared with £186.6 million in 2004.
A full-year operating loss of £62.3 million was in contrast with a loss of £56.5 million in 2004.
The negative impact of restated earnings last year was £1.5 million for the first quarter, £3.17 million for the second quarter and £3.7 million for the third quarter.
IPG awaits the results of a Securities & Exchange Commission probe into an accountancy scandal.
Michael Roth, IPG's chairman, blamed the costs of fixing weak financial systems, resolving accounting issues and attracting talent.