The mayor hopes to deliver 50,000 new homes by 2012
The mayor of London has helped welcome a family into their new home - one of 50,000 new affordable properties he pledged to deliver by 2012.
Boris Johnson unveiled the house in Charlton, south-east London, and took a tour of the Gallon Close site.
He said 20,000 homes have been built since he became mayor in 2008 "despite the huge financial maelstroms".
Minister for London Tessa Jowell said the mayor had taken credit for a scheme started by his Labour predecessor.
Ms Jowell said: "20,000 extra affordable homes are welcome. But the fact is many of these were started under Ken Livingstone's Labour administration. And to be fair, Boris should acknowledge this.
"London's economy needs affordable housing as much as Londoners want affordable homes to live in.
"That's why it's disappointing that the mayor's pledge for 50,000 new affordable homes will be broken, while his proposals on affordable housing mean there will be fewer housing opportunities available to those Londoners who need them most," she said.
The mayor hopes to halve severe overcrowding in social housing by 2012 as part of his London Housing Strategy. About £1bn is invested on the housing project annually.
Mr Johnson said: "Despite the huge financial maelstroms we've had to navigate through, we are on track to deliver more affordable homes in London today than a decade ago.
"These 20,000 homes will change forever the lives of thousands of Londoners. But let's be very clear, this is just the beginning," he said.
Dino Patel, from the National Housing Federation, said the mayor needs to "urgently" meet the need for affordable homes.
"There are more than 350,000 London households on social housing waiting lists," he said.