Mortgage-holders who have been on special rates are being warned they face "significant" payment rises when their current deals expire.

According to new research by personal finance website Fool.co.uk, almost three-quarters of homeowners in Britain will have to adjust to sharp increases in monthly mortgage repayments as the market adjust itself to the ongoing credit crisis.

The findings show that two-thirds of households took out special rate deals two years ago, while one six signed up to special rates 36 months ago.

David Kuo, head of personal finance at Fool.co.uk, said that many homeowners "will feel the full force of the credit crunch when their special-rate mortgage deals come to an end".

He added: "But homeowners can lessen the shock by taking avoiding action now. Paying more than the amount your lender has stipulated while your special rate deal is still in place will chip away at the loan."

The Council of Mortgage Lenders is urging borrowers to plan ahead for higher monthly payments and to shop around for the best deals as soon as possible.