Homeowners have been forced to wipe nearly £3,000 off their asking prices during the peak house-buying season as sellers outnumber buyers by 15 to 1.

The seizure in the UK housing market has pushed the asking price of an average home down by 1.2 per cent to £239,564 during June, according to Rightmove, the property website.

It also emerged today that UK property transactions in the UK slumped by more than a third in May.

About 100,000 deals on properties worth more than £40,000 took place last month, according to estimates from HM Revenue and Customs, down from 158,000 in May last year.

Simon Rubinsohn, chief economist at the Royal Institute of Chartered Surveyors (RICS), said: "These numbers clearly highlight the very real pressure on the residential property market.

"Indeed, the RICS suspects that the level of activity will fall further over the coming months. A drop in property of this magnitude will have an impact on household spending on durable goods as well as on jobs with both estate agent and those working in ancillary areas increasingly under threat."

The parlous state of the housing market was further highlighted by a near-60 per cent fall in the number of new houses being built as home builders struggled to attract new buyers.

The National House Building Council, which has 20,000 registered house builders on its books, said there were 6,890 new starts in the private sector in May, compared with 15,713 this time last year.

However, the lack of affordable mortgages available to new buyers, one of the key drivers of the housing slump, is set to continue, experts say.

Halifax, the UK's biggest lender, increased its rates again at the weekend, while most of the big lenders are now refusing to offer deals to buyers who do not have a large deposit.

The fall in asking prices this month is the biggest decline recorded for June, Rightmove said, and the number of sellers per buyer has doubled since last year when it was 7 to 1.

Howard Archer, chief UK and European economist at Global Insight, the economic consultancy, said: "Against this backdrop, Global Insight forecasts house prices to fall by 12 per cent in both 2008 and 2009, before essentially flattening out in 2010."

He added: "This highlights the fact that house sellers' bargaining power is currently becoming ever more limited and that buyers now very much have the upper hand - if they can afford to buy a house and can get a mortgage."

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