MBNA's £225m credit card insurance account, currently held by Norwich Union (NU), has gone out to tender.
Nine insurers have been invited to bid for what is one of the UK's biggest credit card insurance accounts.
An MBNA spokesman said: "This is part of our normal re-tendering process. Any suggestion that this is because we are unhappy with NU is incorrect and we would regard it as an insult to a valuable trading partner."
MBNA is expected to create a shortlist of three to four insurers by the end of April.
NU confirmed it would be re-tendering for the business.