Controversial Government plans for a huge expansion of house-building in Kent and the south east have come under fresh fire on two fronts.

Environmentalists say the plans for 122,000 more homes in Kent between now and 2026 - 17,000 more than was originally set out in the South East Plan - jeopardises swathes of greenfield land.

In a hard-hitting response, the Kent branch of the CPRE - Campaign for the Protection of Rural England - says the figures for new homes are unrealistic in view of the economic downturn and overlook the importance of safeguarding the environment.

Councils and other groups have been given one last chance to make formal representations over the South East Plan, which will shape the way Kent and the region develops over the next two decades. Consultation ends today and coincides with a warning that house building has slumped in key Kent growth areas because of the recession.

Despite this, the Government is pushing for higher targets, with some parts of Kent earmarked for much larger increases in the number of homes.

Kent CPRE senior planner Brian Lloyd said: "We are concerned that the plan is overly focused on housing, with scant attention being given to its impact on the environment and the infrastructure and services needed to support it. For example, the plan specifically identifies Canterbury and Maidstone as areas where water supply will be a potential constraint to development, but despite this Government expects both councils to plan for 3,000 more homes each than in the draft plan."

He added: "The Government constantly stresses the need to deliver more houses but its proposals for Kent are unrealistic and pay no regard to the fact that house building in the county has currently virtually stopped."

Meanwhile, council chiefs are formally opposing key changes ministers are trying to force through, saying they risk homes being built without any supporting infrastructure like new roads or extra schools.

The South East England Regional Assembly (SEERA) says an attempt to make the targets the minimum figure that the region should get to is an attempt to push up targets through the back door.

SEERA assembly chairman Cllr Paul Carter (Con), also leader of Kent County Council, said a reality check was needed.

"We also need to make Government realise it is unrealistic to increase our annual housebuilding target to a minimum of 33,000 homes a year in the current economic climate. A minimum target means we can’t plan effectively for the land and infrastructure we need - but when developers won’t build homes because they can’t sell them it calls the whole task into question. We need a reality check on housing delivery during the economic crisis."