WWF "in despair" over contents of new Code as it accuses government of backsliding on energy efficiency.
The WWF has resigned from the government's senior steering group for the Code for Sustainable Building.
It said it was "in despair" at the way the office of the deputy prime minister "backslides on energy efficiency and environmental standards for homes".
The organisation said it could no longer sanction the draft of the Code, which will be published next week.
It appears that the recommendations and advice of the Senior Steering Group have been ignored.
Robert Napier, chief executive of WWF-UK
The WWF said that progress had been "agonisingly slow" over the last 18 months, and that the Code being drawn up by the ODPM amounts to the government going back on election pledges.
Robert Napier, chief executive of WWF-UK said: "we have done our very best to work with Mr Prescott's department. It appears that the recommendations and advice of the Senior Steering Group have been ignored, and in a final demonstration of disregard, the members of the Group have not even been given the opportunity to comment on the draft being published on Monday."
The WWF said that the draft Code would drop requirements for new homes to be built close to public transport, and for assessments of the ecological value of development sites. It fears that the draft will also mean that building regulations for energy efficiency will be less strict than at present.