A steering group that includes Shelter and the Federation of Small Businesses leads the campaign group. 
According to the campaign, some 50,000 flats and houses have been granted planning permission each year since 2014.

Jasmine Whitbread, chief executive of London First, who launched the Fifty Thousand Homes campaign, said the figures will be updated every six months. The campaign, she continued, would track London’s progress and “work with planners and developers to get to the bottom of what’s holding up house building in the capital”

The analysis, which was developed by accountant Grant Thornton UK, also part of the steering group, considered the pipeline of housing development and uses Ordnance Survey data. It suggests:

•    The number of homes approved but not built out is increasing, from 28 per cent in 2010 to 36 per cent in 2013.
•    Developments of 100-149 homes are most likely to be built, with 88 per cent either under construction or successfully completed within three years.
•    On average, 30 per cent of new homes being built in London are “affordable” homes, including social housing, affordable 
rent, shared rent and shared ownership.

Graeme Brown, interim chief executive at housing charity Shelter, said: “With renters facing huge housing costs, meaning more young people are packing their bags to leave the capital, there is a mountain to climb when it comes to fixing London’s broken house building system.

“It seems clear that the Mayor of London needs to start getting tough with organisations who have planning permission but simply don’t get on with building the homes that ordinary Londoners so desperately need.

“We are encouraged by the mayor’s commitment to build more homes and make sure they are genuinely affordable. It’s crucial he delivers on those plans if we are to give Londoners a place to call home.”

Sacha Romanovitch, chief executive at Grant Thornton UK, said solving London’s housing crisis could be key to unlocking future growth in the capital at a time when the economic outlook has weakened.

“Additional house building projects in themselves will help to create jobs and stimulate growth, and pivotal to achieving this is working collaboratively with the 32 London boroughs and the City of London Corporation.”

Speaking to The Planner, Annabel Osborne, chair of RTPI London, said: “This new data reinforces the urgency for the mayor to increase the supply of affordable housing, across a range of tenures, in the city. London’s housing need reaches beyond the M25, so his approach must include working with the surrounding regions, particularly the South-East."

She suggested that the mayor should work with planners to identify a series of growth corridors and target them for investment in infrastructure to unlock land for housing and future growth.