The UK business is held by Starcom MediaVest Group, but Heinz contacted rival networks last week as it geared up for a pitch of the business.
Heinz was Starcom's first UK client. It has held the £8 million UK account since 1999, when it beat CIA and MindShare in a pitch.
Michael Mullen, the Heinz corporate affairs general manager, said: "Heinz is doing a European review of its media buying and planning agencies. This in no way reflects the performance of Starcom MediaVest Group in the UK."
He added: "Starcom MediaVest Group has been invited to participate in the review. The purpose of the review is to ensure that Heinz is maximising its media planning and buying efficiencies across Europe and we anticipate that this process will be completed by the end of July."
Leo Burnett, the Starcom Group's sister creative agency, holds the UK creative accounts for Heinz brands such as Salad Cream, Baked Beans, Tomato Ketchup and John West. This relationship is not being reviewed.
Leo Burnett's most recent creative for Heinz was a TV campaign for Heinz's Tomato Ketchup, which broke in April and used the line: "You can't eat without it."