Plans to build 500,000 new homes in the east of England will cause a water crisis, threaten landscapes and destroy wildlife, a new report claims.
Consultants Levett-Therivel say John Prescott's plans for 500,000 new homes will have a serious negative impact.
Hertfordshire and Essex County Councils in particular lack the infrastructure to cope with the proposed increase in population, the report says.
The proposals are due to be agreed at the East of England regional assembly.
The report's author, Roger Levett, said: "Hertfordshire and Essex are already heavily populated and large scale development is going to make infrastructure problems worse."
Alan Moore, Head of Regional Planning and Transport, said "severe affordability problems" for first time buyers in the region have to be addressed.
"We also have to face up to demographic and economic problems," he said.
Areas which take the brunt of the housing include a 'growth corridor' from Peterborough through Cambridge, Stevenage and Harlow, expansion of Milton Keynes and the Thames Gateway Development.
The proposals are due to be agreed on Friday at a committee of the East of England's Regional Assembly.
It is expected to be ratified by the full Assembly on 5 November, before going to a public inquiry.