Bradford & Bingley has been rapped on the knuckles by the Advertising Standards Authority for claiming banks offer higher mortgage rates than building societies.
The ASA has upheld 12 complaints from the public that B&Bs adverts which appeared in national newspapers during its battle to remain mutual earlier this year were misleading and "not necessarily true".
The building society attempted to persuade its members to vote in favour of remaining mutual by claiming banks have higher mortgage rates and lower savings rates than building societies.
The adverts also claimed there would be 93 branch closures and heavy job losses if B&B converted and any profits would be passed to shareholders in the City rather than members.
B&B says its rates and number of branches it has are under review following its decision to hold a formal conversion vote in early 2001 despite 60 per cent of its borrowers voting against Stephen Major's conversion proposal.
B&B press officer Alis Marjoribanks says: "The adverts were never intended to mislead but we accept the ASA ruling and the adverts will never be run again."