Planning reforms 'are confusing'
The government's planning reforms are "contradictory and confusing", a Commons committee has said.
Reforms that introduce a "presumption in favour of sustainable development" are "unsatisfactory" and vulnerable to legal challenges, the Environmental Audit Committee warns.
Ministers say the draft proposals are a vital part of plans to kick-start economic growth.
But campaigners fear the new rules will allow the countryside to be carved up.
In a letter to Prime Minister David Cameron, the committee calls for clearer wording in the draft National Planning Policy Framework (NPPF).
"As it currently stands, the new planning policy framework appears contradictory and confusing," said Joan Walley, Labour MP and chair of the committee.
"It pays lip service to sustainable development without providing a clear definition, potentially leaving future planning decisions open to legal challenges.
"There are environmental limits to how much development any one area can sustain and the government should acknowledge this in the final draft of the NPPF.
"If the new planning framework protects our green belt and countryside, as the government claims, then there should be no problem in defining sustainable development more clearly to avoid misinterpretation."
The government says it wants to simplify Britain's complex planning system, and in the process replace more than 1,000 pages of regulations with 52 pages.
It says the changes are necessary to kick-start house building, which is at levels last seen in the 1920s.
A "presumption in favour of sustainable development" is needed to ensure more homes are built and jobs created, it says.
But critics say this gives a green light to developers. They claim the plans weaken the protection of the green belt and could lead to more urban sprawl and increased numbers of car journeys.
The National Trust, which is among the critics, has previously said overhauling planning rules is "no magic bullet" to boost economic growth.
The body says the committee's recommendations go some way towards addressing some of the key concerns.
But Fiona Reynolds, director-general, added: "Radical changes are needed throughout the draft planning changes if its fundamental flaws are to be addressed and the prime minister's assurance on the role and purpose of planning are to be upheld.
"It's vital that a short-term response to the economic situation doesn't overtake the need for a strong planning system which delivers benefits to communities and the environment as well as the economy.
"The government must resist any temptation to use the current eurozone crisis as a smokescreen for deregulation, which could cause lasting damage to town and countryside for generations to come."
The government says it wants planning system that makes clear its intention to provide homes and jobs, while protecting the countryside.
"The planning system has always enshrined the principle that the economic, environmental and social dimensions of sustainable development should be considered in a balanced way - and it will continue to do so," a Department for Communities and Local Government spokesman added.
The spokesman said the government would take into account the committee's comments, along with input from recent parliamentary debates on the issue.