A shortlist has already been compiled and the process is under way. ASOS is handling the review directly.
The Asos chief executive, Nick Robertson, said at the start of the year that it was looking to "redeploy spend more effectively" after almost doubling its marketing spend in 2013 to £40 million.
Asos has collaborated with Bartle Bogle Hegarty on work including a global digital campaign for the site’s menswear collection in 2011. The microsite, called "urban tour", focused on trends in culture, music, art and fashion from seven cities.
The launch of the review follows that of Asos’s European media planning and buying account, which Campaign revealed earlier this month. Carat, the incumbent, resigned the media business earlier in the year.
Carat created the "#bestnightever" social media campaign in Christmas 2012, in which fashion figures such as Azealia Banks and Ellie Goulding appeared in "shoppable" music videos wearing Asos clothing.
In 2010, Asos appointed Mother as its first advertising agency. The shop created work such as a series of idents for the brand’s sponsorship of the Living TV series Britain & Ireland’s Next Top Model, featuring cats playing fashionistas.
Asos did not respond to requests for comment.