John McFall, Chairman of the Treasury Select Committee, has added his voice to calls for Northern Rock to offer a rescue package to borrowers who took out 100 per cent-plus mortgages.

Mortgages from the bank's so-called Together range comprise a home loan of 95 per cent of the value of the property and an unsecured loan of up to 30 per cent, to a maximum of £30,000.

However, borrowers who come to remortgage face punitive rates of nearly 16 per cent on if they elect to move the secured loan to another lender.

Advisers are calling on the bank, which fell into Government ownership last week, to be lenient with customers on 100 per cent-plus deals as cooling house prices threaten to send some borrowers into negative equity.

Mr McFall told Times Online: "Customers took out mortgages in good faith. Last week I called on the bank to abolish these types of loans. Now that they have done so, I would hope that the company works along with [customers] so they don't find themselves in a tight spot."

David Hollingworth, of brokers L & C, said: "Northern Rock appear to be discouraging mortgage business on the one hand, yet borrowers who then decide to switch face punitive rates. Coventry is one lender that has offered a maturation package for borrowers coming to the end of their 100 per cent-plus deals – it is common sense for Northern Rock to follow suit."

Northern Rock, which now charges a rate of 7.19 per cent on a two-year fix on loans for 95 per cent of the value of the property compared with 5.75 per cent a year ago, took the unusual step last month of sending letters to customers suggesting they look elsewhere for a loan.

One such letter said: "You may wish to arrange a new mortgage deal to avoid paying more than you need to. To arrange a new mortgage deal, we suggest you contact an Independent Financial Advisor who may have access to a wide range of new deals available in the market."

While Together customers can leave their entire loan with Northern Rock when they come to the end of their fixed term, they will face a default interest rate of is 7.58 per cent.

On a loan of £143,000 this will reflect an increase in monthly repayments of £165.52 per month, or £1986 a year.

Another option available to borrowers is to move their entire loan to another provider - however, as all 125 per cent-plus mortgage loans were pulled last week very limited options remain in the 100 per cent loan market. Furthermore, moving the unsecured loan to the cheapest provider on the market would also result in a huge jump in repayments as the loan would have to be repaid over a much shorter loan term – usually seven years compared with a 25-year mortgage.

A spokesman for Northern Rock said: "We are now in a totally different market following the withdrawal of Together and similar products from other lenders this week. We will of course continue to review the options available to existing Together customers in light of these recent developments in the market."

Katie Tucker of Charcol.co.uk, the online mortgage broker, said: "I don’t see how not offering these borrowers a roll-off package equates to treating customers fairly. “

She added: “With house prices cooling, some borrowers who took out 100 per cent-plus mortgages are in danger of sliding into negative equity - when they come to remortgage, they will have a tough time finding another 100 per cent-plus loan.”

“With affordable 95 per cent loan-to-value (LTV) mortgages also becoming less common, there are even fewer options. Mortgage lenders who previously offered these deals need to come up with an alternative for customers who took them out in good faith."