Starcom Motive looks after the United Biscuits business, while Carat handles Jacob's Bakery through the agency's link with Danone. But United Biscuits has instructed ISBA to draw up a shortlist of agencies and is using Billetts to assist it in the review process.
The acquisition of Jacob's in September gave United Biscuits a 27 per cent share of the UK biscuits market.
The review is the latest initiative by United Biscuits since the purchase.
It is also looking at scrapping some conflicting lines or merging them with existing brands.
At the start of the year, Graham Hunter, the Jacob's group marketing director, left, giving Jon Eggleton, his counterpart at United Biscuits, sole responsibility for the department.