AAR CEO Kerry Glazer told PRWeek that chemistry meetings in London should be avoided.
Glazer said: 'What we are saying to clients is it depends on how critical the review is to business. There's a practical consideration when it comes to managing a review through the Olympic and Paralympic periods.
'Simply getting around in London is going to be difficult.'
Glazer said that the logistical issues around the Olympics would compound existing client-side nervousness about the economy: 'You're seeing a natural reticence and general lack of confidence at the moment driven by the recession, with budgets coming under pressure.'
One senior source at a top ten agency said: 'We're taking a cautious view about the level of work and pitches coming in over that period.
'We're thinking perhaps if clients have briefs, they might want to hold them back.'