Some councils have been accused of failing to protect the greenbelt from new development, under new research published by the Campaign to Protect Rural England (CPRE).
The research found that a number of councils are not following planning guidance that allows them to reduce their housing targets if faced with environmental or countryside constraints.
The CPRE said that while local authorities such as Brighton, Watford, Hastings and Crawley have reduced their housing targets by 50% or more, others are pursuing the full Objectively Assessed Need (OAN) despite a high proportion of their land being protected countryside.
This includes Christchurch and East Dorset, which is pursuing its full OAN target of 8,490 houses over 15 years, despite 84% of the area being covered by greenbelt nature conservation land.
CPRE's planning campaign manager, Paul Miner, said: 'Government planning rules state that councils should reduce their numbers if faced with significant constraints. A number of councils around the country have done just this. One has to ask, therefore, why the Government is allowing councils to ignore national guidance in places such as Maidenhead.
'We need to build more genuinely affordable homes. But current rules promote urban sprawl and cause the unnecessary loss of countryside. A more transparent and less damaging method of planning for housing is urgently needed.'
However, Christchurch and East Dorset Borough Councils have said councils do not have the legal power to reduce their assessed needs figure.
Strategic director of the councils David Barnes said: 'Approximately 60% of the 8,490 dwellings will be delivered on brownfield urban sites and we calculate that only 0.6% of the greenbelt will be used to deliver housing during the plan period. Meeting these conflicting needs requires a balanced approach and I believe we have achieved this in our Local Plan.'
