Last year, the US fashion retailer launched a European office with the aim of creating marketing that caters to local tastes. It hired Clare Dobbie from advertising agency Mother as its European marketing director.
Dobbie confirmed that Naked would be working with Gap's media agency, ZenithOptimedia, on "customer segmentation". She denied the move would lead to specific advertising being produced for the European market.
Gap's global advertising is currently handled by US agency Laird and Partners. The retailer spends about £10m on advertising in the UK and more than £60m across Europe.
Gap's international operation has been struggling recently. Earlier this month the company revealed that like-for-like sales in its overseas stores had fallen 11% for the first quarter, ended 29 April. The figures mirror those in the US, which have fallen by 8% over the same period.
Gap has come under increasing pressure from discount retailers and supermarkets. Last week it emerged that Tesco is working on an upmarket fashion range.
In the US, Gap's marketing share has been hit by rivals American Eagle and Abercrombie and Fitch.
The chain has about 3100 stores worldwide and analysts have suggested that its size has meant it has had trouble responding to customer trends.
In addition to opening a dedicated European office, Gap has launched a similar operation in Japan.
In February, Gap international vice-president Andrew Rolfe left the company following its decision to decentralise its operations.
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