Customers who have mortgages with lender Northern Rock have been told they have no reason to be concerned about the loan given to the firm today by the Bank of England in order to help it through the current credit crunch.

Chancellor Alistair Darling authorised the loan today to give Northern Rock a chance to work through problems caused by the knock-on effects of the sub-prime lending crisis in the US but financial experts said it is important for the public to remain calm.

"Consumers need to understand that the problem for lenders generally at the moment is in raising funds, not in lending quality," said the director general of the Council of Mortgage Lenders, Michael Coogan.

Melanie Bien, a director at mortgage broker Savills Private Finance told Reuters: "If you''ve got a mortgage with Northern Rock, there is nothing to worry about as you shouldn''t be affected."

Other institutions have felt the effects of the current economic turmoil, with both Halifax and Abbey deciding to raise the rates on their tracker mortgages in recent days.