The Government's new house-building targets represent a serious long-term threat to countryside of Hertsmere, the House of Commons heard last week.
Hertsmere MP James Clappison called on the Government to change its policy on building new homes in the South-East during a debate on Wednesday.
Two weeks ago the Government announced that 3,280 new homes would have to be built in Hertfordshire for each of the next five years to satisfy demand.
But Mr Clappison told fellow MPs it was unlikely large numbers of new homes could continue to be provided in Hertsmere without the use of Green Belt land.
"A point has been reached where development on this scale represents a serious long term threat to the Green Belt," he said.
The Government has announced that it wants as much as possible, around 60 per cent, of the new housing to be built on previously-used sites.
While he welcomed this idea, Mr Clappison claimed it was not practical to suggest so many derelict sites could be found for housing in Hertfordshire.
He warned that the character of existing towns in Hertfordshire could be harmed as planners struggle to find disused land for new homes.
"The development which is being set in train is at the expense of the environment we will be handing on to future generations," he said.
"It is bad for the quality of life of future generations as open spaces disappear and it is bad for the environment itself, as habitats, plants and animal species are lost," he said.
Mr Clappison urged the Government to continue the debate on housing in the South-East to find a way of protecting the countryside from development.