THE Government last night stepped into The Northern Rock crisis in a bid to restore confidence in the beleaguered bank, which saw another £600m wiped off its stock market value yesterday.

Chancellor Alistair Darling said the Government would guarantee the deposits of Northern Rock savers.

His intervention came after an unprecedented day that saw hundreds of millions wiped off the stock market value of some of Britain's biggest banks.

Mr Darling hoped the move would halt the stampede among customers trying to withdraw their money from the embattled bank.

More than £2.5bn has now been withdrawn by panicking savers since Northern Rock applied to the Bank of England for emergency funding last week.

Earlier, pleas for calm fell on deaf ears as savers queued to withdraw their money and investors desperately off-loaded Northern Rock shares.

Northern Rock shares were down 40 per cent at one point yesterday, recovering slightly to 35.4 per cent lower by the close of business as fears continued to grow for its future.

There were signs the panic was spreading to other banks.

The Alliance and Leicester also saw a collapse in its stock market value as shares spiralled into the red by more than 30 per cent.

Bradford and Bingley suffered a 15 per cent drop as worried investors moved money out of the banking sector.

Stock market traders will be hoping for some relief from the US Federal Reserve, which is expected to announce a cut in interest rates today. They are keeping their fingers crossed that a cut will help restore confidence that the global economy is not heading towards a recession.

The Government's announcement last night that it would guarantee all savings in Northern Rock accounts was seen as an indication of how serious the situation has become.

People are already protected by the Financial Services Compensation Scheme, but anyone with more than £2,000 could lose some of their savings if the bank goes bust.

Mr Darling said that people could continue to take money out of the bank, but that if they chose to leave it there, it would be secure.

The decision to guarantee all deposits came, he said, because he wanted "to put the matter beyond doubt".

In a separate move to restore confidence, the bank published adverts in leading newspapers - including today's Northern Echo - to reassure customers.

It says: "Your money is safe with us. If you want some or all of it back you will get it back. But if it stays with us it is secure.

"These have been troubled times but Northern Rock will prevail, we will not let you down."

Northern Rock's share price tumble has now nearly halved the bank's market value to £1.19bn since it agreed emergency funding facilities with the Bank of England last Friday.

The group was the most heavily traded stock on the London market yesterday, with the hurry to off load shares in the firm leading to ''exceptionally high'' trading levels, according to the London Stock Exchange.

Shares in the group closed at 282.75p, down 155.25p - just over one-fifth of their value in February.

Several banks were rumoured to be stalking Northern Rock last night with a view to buying its assets.

But brokers at Citigroup cautioned the bank might now struggle to find a buyer, despite being a cheap pick for any possible acquirers.

Citigroup said: With an almost complete lack of earnings visibility beyond 2007, a damaged brand, a large balance sheet and a lack of synergies, we do not envisage a long queue of potential bidders.

Northern Rock's woes depressed fellow mortgage lenders as investors feared the impact of the ''credit crunch'' in money markets could spread to other lenders.

Alliance & Leicester was the hardest hit, with fears surrounding the stock despite assurances from the group that it was ''business as usual''.

Specialist lender Bradford & Bingley also suffered, falling 15 per cent. Halifax parent HBOS, another big player in the mortgage sector, fell 5 per cent, while ABN Amro rival bidders Royal Bank of Scotland and Barclays were also down by 4 per cent and 3 per cent,

Housebuilders also suffered steep falls amid market concerns that more expensive mortgages stemming from Northern Rock's difficulties could put the brakes on the housing market.

Blue-chip housebuilders Barratt Developments and Persimmon both fell by 7 per cent. In the FTSE 250, Redrow, endured a 7 per cent drop and Taylor Wimpey shares shed 5 per cent.

Rob Jones, senior lecturer in accounting and finance at Newcastle University Business School, said house prices may now fall.

"Banks will be less keen to loan to people, and be more careful about who they lend to. That will result in a reduction in the demand for housing.

"If demand falls, and supply doesn't change, basic economics tells you prices will level off or fall. There could be some negative equity."

Howard Archer, chief UK economist with Global Insight, said: ''Extensive news coverage of people queuing up to withdraw their savings from Northern Rock could well fuel the fears that other financial institutions will be affected and increase general concern about the economic outlook.''