Briefs have been sent out to agencies and pitches are planned for next week. There is no formal incumbent on the account.
The review is likely to cover online CRM after Thomas Cook’s marketing and e-commerce director, Mike Hoban, recently revealed that the business was moving to a more digitally focused model with an "always-on" strategy.
A Thomas Cook spokesman said: "Unfortunately, we can’t comment on rumours or speculation, and have nothing to say at this time."
Thomas Cook returned to TV advertising in June with a campaign that was fronted by the actor James Nesbitt, and included CRM and direct marketing elements.
In October, the company dropped its long-running "Don’t book it, Thomas Cook it" slogan, replacing it with "Let’s go" and a heart-shaped logo. Carat Manchester handles Thomas Cook’s £12 million above-the-line media account, which moved from Arena in March. Carat Manchester also runs the £15 million digital media business.
A review for Thomas Cook’s creative account kicked off in March. The incumbent is Havas Worldwide London.
Havas Worldwide created the summer campaign, but Thomas Cook has not confirmed which agency will handle activity for the key Christmas period, which is also likely to feature Nesbitt.