In July, the Deparment for Communities and Local Government announced plans to make the new PD rights, which allow offices to be converted into homes without the need for planning permission, permanent. They were introduced last May for a temporary three-year period.
In September, during the mayor’s question time, Johnson pledged that "thermonuclear weapons will be used" against the DCLG proposal, which was then undergoing consultation.
But a motion passed today by the assembly said that Johnson "did not go far enough and failed to fulfil his pledge".
The motion said that the PD rights "should not be made permanent", adding: "Bringing in permitted development on office space and other employment uses, such as light industry and warehouses, represents a threat to London’s economic recovery."
Labour Party assembly member for Barnet and Camden, Andrew Dismore, who proposed the motion, said: "The mayor’s response to these dangerous government proposals has been more pop gun than thermonuclear device.
"It’s time Boris worried less about constructing a colourful turn of phrase and more about backing up his promises with real action in defence of London’s vital economic interest against these dangerous government proposals"
In response, the deputy mayor for planning, Sir Edward Lister said: "The mayor and I are keeping up the pressure on government and have met with the planning and housing minister to advise him that changing these regulations threatens to undermine this crucial mix and damage the economic prosperity of London and the UK as a whole.
"The mayor has always recognised that, overall, London has surplus office space.
"He believes that the release of this space must be managed carefully through the planning system so it does not undermine viable employment capacity."
Lister added that maintaining a stock of "quality office space in key commercial areas" was "vital" to the capital’s success.
A webcast of the assembly meeting can be viewed here.