The government has clamped down on the number of schemes that will be eligible for assessment under the 2002 version of Part L of the Building Regulations, which deal with energy efficiency.
The ODPM has announced that buildings must have their full plans approved by 6 April if they are to be assessed under these regulations, which are more lenient than the upcoming revised Part L.
It had previously been thought it would be possible to indicate just the scope of a project to Building Control before this date.
The ODPM also announced that the transitional period for implementing the regulations has been cut from three years to one.
Industry insiders said the rule meant any scheme submitted now would probably not receive approval by 6 April as there was more work to do on each application.