Green groups have warned ministers they could be acting unlawfully if they watered down current commitment to the 'Merton Rule'.
This is the planning requirement for developers to ensure that a proportion of energy use in new developments comes from on-site renewables.
This regulation is known as the Merton Rule after the London Borough which first drafted the condition. The warning came in a letter from the Sustainable Energy Partnership which claimed that under section 82(5) of the Energy Act 2004 the relevant Secretary of State has a duty to implement the microgeneration strategy drawn up by the administration as a result of that legislation.
In a letter to planning minister Yvette Cooper the green groups pointed out that the microgeneration strategy called for a tightening of the Merton Rule. As a result the Partnership has argued that any weakening of the Merton Rule in forthcoming revised Government planning advice would be "ultra vires".
Dave Sowden, chief executive of the Micropower Council, said: "Any suggestion of a u-turn in this important policy is likely to knock the confidence of investors and seriously call into question both the Government's political commitment to this sector, as well as whether it has fulfilled its legal duty to implement the microgeneration strategy."
The Partnership represents all the major environmental and fuel poverty non-governmental organisations and relevant trade associations.
A spokesman for Cooper's department, Communities and Local Government, said the concern was misplaced. "This is a lot of nonsense - there is no u-turn on Merton. Councils will continue to be able to use their Merton rules but we want them to go even further where sites allow for greater levels of renewable energy."
In a related development the Royal Town Planning Institute issued a statement in support of the Merton Rule and the principle of using local planning policy innovations to achieve reductions in emissions of carbon dioxide, the main greenhouse gas.
"There is a role for the Merton Rule's objectives to be taken up by national policy, but this should not prevent ongoing innovation at a local level," said Rynd Smith, director of policy and communications with the RTPI.
