Cheeky bosses from the Bradford-based Yorkshire Building Society have come up with a mortgage to poach customers from the Bradford & Bingley.

The Yorkshire, which becomes Britain's third-largest building society to the Nationwide and Britannia when the B&B converts to a financial plc in December, has set up a Mutual Mortgage in an attempt to entice B&B customers. The mortgage offers a one per cent discount to B&B mortgage-holders.

But a spokesman for the Bradford & Bingley attacked the move as unfair. He said: "The Yorkshire is a mutual building society and as such it should be offering the one per cent discount mortgage to all its members not just to Bradford & Bingley customers."

The move follows a decision by Bradford & Bingley members to convert to a financial plc - in effect a bank - which will result in higher interest rates for borrowers - including mortgage-holders - and lower rates for savers.

Iain Cornish, the Yorkshire's secretary and general manager, said: "A typical borrower has already paid Bradford & Bingley £250 extra in the form of higher mortgage payments and it will not be long before the balance of any conversion payment is clawed back - a windfall with a rotten core."