House builders stand accused of jumping the gun to concrete over the countryside before Government housing targets have been agreed.

Ministers believe almost 600,000 homes should be built in the West over the next 20 years, at least half of which will have to be built on fields.

But with the economy in dire straits, critics say the figures are a gross overestimation.

A decision is not expected until May. However that has not stopped developers rushing to stake their claim on green fields.

House builders have applied to build at least 8,400 homes in the region on greenfield and even green belt land earmarked for homes in the draft Government plans. Some have gained outline permission on appeal.

Campaigners fear once permission is granted, it will be hard to reverse, even if it later emerges the homes are not needed.

They are jumping the gun by years potentially," said Cheltenham MP Martin Horwood.

"Some of these developers have already got nine- tenths of the way through the planning process while we are still fighting. It's appalling. At this rate, even if we win our battle to have the number of homes reduced, it will be too late to save many green fields."

Mr Horwood and five fellow West MPs will meet with Local Government Under-Secretary Iain Wright in Westminster to express their concerns.

At the heart of the debate is the draft South West Regional Spatial Strategy (RSS), a plan setting out how many homes will be built over the next 20 years and roughly where. The original draft proposed 461,200 new homes by 2026, equivalent to 23,060 a year.

But following an examination in public before an independent panel, the Government proposed to bump up the target by 29 per cent to 592,460.

The new figures met unprecedented protest. The South West Regional Assembly and the Royal Town Planning Institute South West (RTPI) are among the many bodies claiming the Government has got its sums wrong.

The RTPI's South West policy officer Dr Geoff Walker said: "The Government is hell-bent on getting three million houses built nationwide and appears to be doing all it can to crank up local numbers without proper testing or proper evidence."

But developers say they have had to wait long enough. Colin Lewis, regional chairman of Redrow Homes, which has not yet submitted a greenfield RSS application, said: "It is perverse for local authorities to seek to impede planned beneficial development when unemployment is rising rapidly and investment has fallen dramatically.

"Local authorities should grasp any opportunity to bring forward development irrespective of whether it is on brown or greenfield land. The local councillors need to encourage new investment to reduce the impact of the recession and protect jobs by providing new homes."

The place where most planning applications on greenfield sites have been lodged is Tewkesbury in Gloucestershire.

Outline plans for 570 homes on fields at Longford were allowed on appeal last summer as was an application for 450 dwellings on fields in Bishops Cleeve and another for 360 homes on an old sports ground and green belt land at Badgeworth, although this one was already allocated in the council's plan.

Builders have also applied for permission for 1,750 homes on green belt land at Innsworth.

Councillor Bill Whelan, who represents the parish said: "Developers are jumping the gun on this issue.

"Everyone wants a total review of the RSS housing numbers, especially in light of the recession but also in light of what happened in July 2007 which shows this area is prone to flooding.

"Everyone realises we have to have some houses built, but when and where these houses are built should be a matter for local authorities to decide, not the Government."

The villagers of Leckhampton, near Cheltenham, feel under siege as our report (left) shows.

And on the outskirts of Cheltenham, a High Court challenge has begun over outline plans to build 44 homes on a greenfield site in an area of outstanding natural beauty in Charlton Kings.

In North Wiltshire, there are applications for greenfield sites in Calne and north-east of Swindon.

In Taunton Deane, there are applications at Bishops Hull and Nynehead as well as for 900 homes at Monkton Heathfield where an appeal was upheld by the Secretary of State.

Up the road in Bridgwater, developers have applied to build 2,000 homes, although part of this will be on the site of the old cellophane factory.

North Somerset Council is expecting its first application in spring for a 10,500-home new town on green belt land south-west of Bristol. In South Gloucestershire, developers have asked for outline permission to build 1,200 dwellings at Harry Stoke with access in the green belt. The council turned the application down but the developers used the RSS figures at the appeal stage and the outcome of a judicial review is awaited.

At Frampton Cotterell, developers applied to build 220 houses on a greenfield site at Windmill Green, but were turned down.

Ministers declined to answer specific questions but a spokesman for the Department of Communities and Local Government said: "The South West is facing long-term housing shortages and affordability issues. It is already the only region with above-average house prices and below-average incomes. If more homes are not built, the housing ladder will get even further out of reach leaving the next generation with nowhere to live."