The AJ understands that the new Part L of the Building Regulations will be published on 16 March, before becoming law on 6 April.
And a source close to the document's publisher has told the AJ that the finalised Part L will have 'fundamentally different content' to the previous draft, which was unveiled in August.
It is this draft that all architects, engineers and building-services experts have been using for months to aid their designs.
But it is believed that significant changes to this document are still being worked on by officials in the ODPM, who are rushing to hit the March deadline because of the threat of a fine from the EU if it is published any later.
It is anticipated that these radical changes will cause severe problems for anyone lodging a planning application over the next few months.
Part L, a four-document publication, regulates the levels of energy efficiency that need to be met by new buildings through such measures as insulation and combination boilers.