Simon Hughes MP has called for the public to be given the right to challenge local authorities which grant planning permission for developments that fail to meet the council's own affordable housing quota.
Speaking at the London Liberal Democrat conference held at London South Bank University on Saturday, Mr Hughes said: "Time after time, the Labour council here in Southwark side with private developers over local residents.
"Failing over and over again to insist on affordable homes in new developments – not even meeting their own policy of at least a third of all new homes being affordable.
"I am clear we should be more ambitious – and aim in every London borough which needs this for half of our new housing to be affordable – and all advertised locally first.
"And we need to go further: I want the public to have the power to appeal where their council breaks their own affordable housing commitment.
"I want it to be easier for councils to be able to use homes which are left empty.
"I want to see developers' economic viability assessments for housing developments made available to the public from the time of planning applications – so we can be the judge of whether they are fiddling the figures.
"And I want to see the National Planning Policy Framework changed to prioritise housing need over housing demand."
Neil Coyle, Labour's prospective parliamentary candidate for Bermondsey & Old Southwark, poured cold water on the Lib Dem incumbent's speech.
He said: "Southwark needs MPs who stand up for our borough and are focused on people's priorities here.
"Sadly the local Lib Dem MP in Government with the Tories has decimated funds to help build homes, has redefined 'affordability' and given us a Help to Buy scheme which helps no one in the constituency.
"If I win in May I'll be helping deliver Labour's commitment to 200,000 homes a year by 2020, which includes extra help to build social housing.
"I'll also be lobbying for a Housing Growth Area here to ensure local people get prioritised when new affordable housing is built.
"These concrete measures offer more to local people than Lib Dem Hughes' belated statement after years of neglecting the issue."