Britain's house price growth will be halved next year as the global financial crisis exacerbates the impact of rising mortgage rates, according to Nationwide, the biggest mortgage lender.

After the dramatic bail-out of high street bank Northern Rock underlined the impact of the American 'sub-prime' mortgage crisis on Britain's financial sector, Fionnuala Earley, Nationwide's group economist, said she expected house price inflation to slow to around 3 per cent next year.

Thousands of anxious customers queued outside Northern Rock branches for a second day yesterday, ignoring calls for calm from the Chancellor, Alistair Darling, and the bank's management, and sparking fears of a full-blown 'run' on the bank.

Speaking to Channel 4 News last night, Darling said he had been assured by the Financial Services Authority that Northern Rock was capable of meeting its financial obligations to its customers.

In the first signs of political fallout from the crisis, David Cameron accused Gordon Brown of failing to rein in public and private borrowing over the last decade, saying the nation's economic growth is based on a 'mountain of debt'. Writing in today's Sunday Telegraph, the Tory leader says: 'This government has presided over a huge expansion of public and private debt without showing awareness of the risks involved.

'Though the current crisis may have had its trigger in the United States... under Labour our economic growth has been built on a mountain of debt.'

House price growth was running at just below 10 per cent in August, but Nationwide believes it will have dropped to 7 per cent by December and continue slowing throughout next year.

The worldwide credit crunch that pushed Northern Rock to the brink of collapse could make a housing market slowdown worse, Earley warned. 'I think all it can do is make it [the market] cooler: that comes through sentiment, and through expectations.'

With base interest rates at a six-year high of 5.75 per cent, economists said that the feelgood factor was already evaporating and that the Northern Rock crisis could deal a fresh blow to confidence.

'This confirms some of the fears that people had, and reinforces the idea that they need to be more circumspect, and that money is tighter,' said Richard Hyman, director of retail research firm Verdict.

'It couldn't have come at a worse time: consumer confidence was already heading south,' said Kevin Hawkins, director general of the British Retail Consortium, though he added that, as long as Northern Rock was the only casualty, the effects could be short-lived.

A report from property website Rightmove, released on Friday, showed that property prices fell in the last month for the first time in three years. It is expected that, although there will be overall growth in the housing market, some areas of the UK could suffer significant price decline.

Meanwhile, Northern Rock apologised to customers last night, saying it was 'disappointed to see uncertainty caused'. The apology came amid growing speculation of a takeover bid, with HSBC and Lloyds TSB both being mooted as potential suitors. Insiders are predicting that a takeover could occur within weeks to secure the bank's future. One plan currently being looked at by City bankers is to divide the company's £100 billion mortgage portfolio between some of the major banks.

Savers have been rushing to pull out their cash since it emerged last Thursday that Darling had sanctioned an emergency loan from the Bank of England to prevent Northern Rock going bust.

One couple had even camped outside Northern Rock's Cheltenham branch in Gloucestershire overnight, desperate to withdraw the £1m proceeds of a house sale. 'We were told that because our money was in an online account we wouldn't be able to withdraw it there and then,' said Fiona Howard. 'That money is our lifeline, as we are living in rented accommodation at present.'