The IPS is currently weighing up the benefits of centralising the European account, but has not completely ruled out keeping separate agencies.
As well as Vizeum in the UK, the media business is held by local media agencies in Germany and France.
The £35m UK account is worth more than the other European accounts because the UK is the second-biggest market for AOL services besides the US.
The review is a result of a shake-up at AOL's marketing department, which saw the resignation of vice-president of marketing Sharon Lang in January, with Orange marketing manager Timothy Ryan taking up the new role of brand director.
AOL's creative agency Grey London is unaffected by the review.
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