Pleas from Hammerson and British Land for more than £1.3 billion from shareholders this week are expected to open the floodgates for a host of similar moves as property firms cope with tumbling prices.

After an eye-watering £1.7 billion writedown of its portfolio, Hammerson needs almost £600 million to avoid a possible breach of its banking covenants.

British Land, meanwhile, wants £740 million to shore up its balance sheet, as well as giving it the chance to buy up cheap assets from distressed sellers.

Investors may have to get used to the begging bowl being handed round, as the lack of debt financing available from banks for potential buyers means property sales are less certain and negotiations protracted.

The sector's latest dash for cash marks yet further fall-out from the credit crunch, which culminated in last autumn's banking crisis.

Both Hammerson and British Land had been selling assets to raise debts before the near-meltdown of the financial sector made disposals much more difficult. Their rights issues are therefore heavily discounted to tempt in as much investor support as possible.

"Although initially starting as a banking issue, the negative consequences of the credit crunch for the broader economy have become increasingly clear over the last few months," British Land said.

It has written off more than 20% of its portfolio value in the past nine months, as the "extreme turmoil" in capital markets caused a "current dislocation in asset prices".

Hammerson's cash call was unveiled on the same day British Land sold a 50% share in its Meadowhall shopping centre in Sheffield in a deal valuing the overall development at £1.18 billion.

At first glance this seems a tidy sum - and it exceeded the depressed expectations of the market - but it represents the virtual erosion of years of value built up in the boom. British Land bought Meadowhall for £1.09 billion as far back as 1999. The centre was valued at around £1.6 billion just 18 months ago.

The current struggles of the sector are far removed from the fever-pitch excitement which greeted the launch of real estate investment trusts (REITs) in the UK two years ago.

Investors were enticed by the higher dividends promising the end of a tax regime that saw property firms effectively taxed twice - sparking a rush of companies to spin off their property holdings into the tax-efficient property vehicles.

But the Royal Institution of Chartered Surveyors (RICS) predicts the current market carnage has far further to run. It forecasts that commercial property values could fall a further 25% over the next two years, which would take the fall in cumulative fall in prices to 50% since June 2007 - a downturn worse than those of the 1970s and early 1990s.

Its latest gloomy data, published this week, show available space rising across all regions and sectors for the first time in the survey's history during the final quarter of last year - most rapidly in London and the South-East, which saw the biggest rise in incentives to tenants.

The findings come on top of similar miserable figures from consultant Jones Lang LaSalle which revealed a record 12.8% fall in total UK property returns during the last three months of 2008.

Capital Economics property expert Kelvin Davidson said the RICS data underlined just how weak the demand for floorspace had become. The only "positive" he could find in the figures was that the rapid scaling back of development pipelines could limit the impact of falling rents.

"We continue to expect a deep and prolonged economic recession to drag down commercial property rents by at least 10% both this year and next," he added.

So how much will firms need to raise to cope with the bleak economic environment? Analysts at JP Morgan estimated that the top six - Hammerson, British Land, Land Securities, Segro, Brixton and Liberty International - may have to raise more than £4.2 billion to bring their balance sheets back to health.

But making estimates is not easy given the current uncertainty of the market. When Hammerson set the ball rolling, Citigroup's Harry Stokes said it was "impossible to forecast" whether the boost to its finances would be enough.

While asking shareholders for cash is an unpopular move at the best of times, it is a far cheaper alternative than risking a breach of lending terms. "Renegotiating bank covenants would have been extremely expensive", Mr Stokes added.

The property sector's heavy reliance on debt - an unwelcome characteristic in the current environment - is underlined by the latest available figures for the top six companies, showing a combined £21 billion in net debts between them.

But the City has been largely supportive of the rights issues. Charles Stanley analyst Tina Cook said: "The sector in general is still facing headwinds mainly due to banks' reluctance to lending and making their own property writedowns."

With firms unwilling to dispose of their best assets in the current environment, the fundraising could buy struggling companies some time and provide a chance for opportunistic purchases, she added.

"The companies will want some firepower so they can buy at the bottom of the cycle," Ms Cook said.

In these bleaker times, even the REIT model is now no longer looking as appealing as Revenue officials have thrown out calls for the vehicles to be able to pay dividends in shares instead of cash.

This looks to have shut down a further option of capital conservation available to other struggling sectors.

And in an ironic reversal of fortune, it seems the demands on shareholders to pump funds back into the very same companies is set to gather pace as the UK's recession deepens.