The jobs of up to 15,000 estate agents are under threat if house sales show no sign of recovering, industry experts fear.

Since the property market peaked in July last year, between 5,000 and 7,000 estate agents have lost their jobs, either through employers' staff cuts or through resignations as employees struggle to live on a basic salary without commissions.

With housing sales down 50 per cent, industry estimates indicate that as many as half the country's 30,000 agents could be looking for work before any sign of an upturn occurs in the housing market.

Chris Wood, president-elect of the National Association of Estate Agents, who owns an estate agency business in Helston, Cornwall, said: “If you take the worst-case scenario that housing sales have fallen by 50 per cent, then you would expect the industry to lose 50 per cent of its people. It's something of a Darwinian process. Although there are, sadly, some very good firms going to the wall, most of the ones closing are those that came in at the height of the boom that didn't really know their business.”

Countrywide, Britain's biggest estate agency and the owner of the Mann, Bairstow Eves and John D. Wood businesses, is the latest agency to attract concern after Standard & Poor's downgraded Countrywide's credit rating, saying that it could run out of cash in the next 12 months.

Grenville Turner, Countrywide's group chief executive, wrote to the compay's 8,000 staff yesterday to reassure them that the business was robust. “At the end of [the third quarter] we had around £106 million of cash on our balance sheet to protect us from the impact of this market, which I suspect is more than all of our competitors put together. We intend to keep it that way,” he wrote.

However, he told staff that the company would continue to take tough decisions to close offices and reduce staff numbers, to make sure that it remained viable.

Other high-profile estate agency names have had problems, including Humberts, which was the first leading estate agency business to collapse over the summer. Halifax has closed 50 of its estate agency offices, while other local names around the country have been forced into mergers, administration or liquidation.

Jeremy Helsby, chief executive of Savills, said: “If the volume of sales continues to fall, there is simply not enough business to go round. If sales are down by 50 per cent, then there will be 50 per cent less income.”

Savills has already let estate agents and surveyors go, but it will not confirm the full extent of departures. It has closed one office outside London and is considering the possibility of closing more.

Yet Savills, like other estate agency groups, is reporting strong growth in its lettings business, particularly in London. “There is a new breed of people renting, with people who have sold their properties sitting on the fence hoping that values will fall further,” Mr Helsby said.

Foxtons, which was sold by Jon Hunt, its founder, at the top of the property market last year for £360 million to BC Partners, the private equity group, is considered to be vulnerable because of its high levels of debt. Its new owner is in talks with the bankers who funded the deal by putting up more than £250 million.

Sources close to the chain denied that it was experiencing difficulties, saying that it had enjoyed strong growth in its lettings business and had advertised recently for new recruits.

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