House prices could fall by 25 per cent if the credit crunch persists, with the market declining by 10 per cent this year and by a further 15 percentage points in 2009, a new study suggests.

The pain will be felt in all but the most exclusive postcodes, according to Savills, the estate agent.

However, action by lenders could limit the credit crunch impact to a slide of 6 per cent.

Savills’s revised forecasts coincide with figures from Hometrack, the property data business, showing that house prices have dropped a further 0.6 per cent in the past month, the seventh consecutive fall.

Estate agents polled by Hometrack said that prices are 0.9 per cent lower than a year ago.

The worst-affected areas are in East Anglia, the West Midlands, Greater London and Wales.

Prices are now sliding in 51 per cent of postcode areas; a month ago they were falling in only 28.8 per cent of areas. Agents say that it now takes nine weeks to sell a house; a year ago it took only about six weeks.

Buyers are achieving 93 per cent of the asking price on average.

Yolande Barnes, Savills’ director of residential research, said that if home loans were to become more freely available soon, prices could be a mere 4 per cent lower by the end of this year and ease by another 2 per cent in 2009. But she gave warning of greater difficulties if the banks did not end the mortgage drought.

“It could have very serious consequences for the national housing market and economy in general,” she said.

Amid the turmoil elsewhere in the country, demand for London houses costing above £5 million is likely to continue unabated, with international buyers having no need to borrow. Last week, the would-be buyer of a £25 million mansion was gazumped.

A divide is opening between what Ms Barnes terms the “super-wealthy” and the “merely wealthy”. City executives in the latter group fear job losses and, like everybody else, are struggling to secure home loans.

As a result, prices for London properties between £1 million and £2 million are under pressure and could fall by as much as 16 per cent.

Eventually the whole market should recover from a severe downswing – but slowly, Ms Barnes said. She believes that there could be a bounce-back by 2012, with lower prices making property more affordable.

The continuing shortage of homes in most regions should lend support to prices.

Construction companies such as Persimmon, which are suffering from the credit crunch, are already downing tools, which will aggravate the shortage of property.

Ms Barnes is the latest commentator to revise downwards her predictions for 2008, taking into account the bleaker economic outlook and the withdrawal of credit.

Knight Frank, another leading estate agent, has revised its forecast from a rise of 3 per cent in property prices this year to a fall of 3 per cent.

Ms Barnes assessed the chance of a 25 per cent slump at 40 per cent and a 6 per cent slide at 60 per cent. The gloomier scenario is based on job losses spreading beyond the financial sector to other industries such as housebuilding.

She said: “There are some sites on which homes were to be built which are no longer viable unless the construction company can renegotiate the deal.”

In recent weeks the banks, scarred by sub-prime debt, have become even more reluctant to lend to homebuyers. Household finances are also under strain from higher energy, food and tax bills.

Last week, the Bank of England extended a £50 billion bailout to the banks, but this has yet to be passed on to borrowers. On Friday Halifax increased the cost of some of its deals by 0.6 per cent.

Richard Donnell, director of research at Hometrack, said: “Weak confidence is effectively resulting in a ‘buyers’ strike’ with households sitting on the sidelines and waiting to see how events unfold.”