It’s disappointing that both Sadiq Khan and Zac Goldsmith in their campaigns to be London’s next mayor have pledged to leave London’s green belt untouched. They appear to have capitulated to the outer London countryside lobby without even the hint of a fight and have condemned a whole generation of Londoners to a miserable housing future.

Khan promises to “protect the green belt, green spaces and play spaces, prioritising development on brown field sites”, and to “oppose building on the green belt, which is even more important today than it was when it was created.” Goldsmith talks about “protecting the green belt from development.”

Yet all the available evidence suggests that London’s immediate housing crisis will not be solved within its existing footprint and that selective growth into the green belt is the only medium and long-term option.

Their green belt commitments are also premature, given that George Osborne is about to announce a programme of garden suburbs and that Crossrail could open up opportunities for sustainable development on green belt land.

Greater London was created in 1965. Since then its population has grown to over 8.6 million and is set to increase to 10m by 2030 and possibly 11m by mid-century. That means up to a million new homes will be needed over the next 15 years to bridge the gap and make up for past undersupply – that’s 66,700 each year. The Greater London Authority’s (GLA) own calculations suggest that London needs to build up to 62,000 new homes every year. Both Khan and Goldsmith have pledged to build 50,000 homes a year.

Can this growth be accommodated on brownfield land? No.

Finding a completely accurate figure for available brownfield land is difficult, since boroughs do not keep decent records. When a Freedom of Information request was made recently, 15 of the 32 London boroughs either failed to respond or said they held no information.

But a recent study by respected planning consultancy Nathaniel Lichfield & Partners found that brownfield land would provide only half of London’s needs over the next 15 years. To be precise, only 365,731 homes out of a required 788,568 could be fitted onto brownfield land. That’s just seven years’ supply assuming 50,000 homes a year. Where does the rest come from?

The Homes and Communities Agency claims that there are 64,000 hectares of brownfield land in England as a whole, which would be enough for 2.6m homes but much of it is unsuitable for development due to being in the wrong place, heavily contaminated or better used for non-housing use. Nathaniel Lichfield & Partners estimate that this land would provide little more than a million homes across England as a whole.

Savills is working on a more comprehensive record for London but the Mayor has recently published an interactive map of 40,000 publicly-owned sites which, he says, could provide 130,000 homes. But if you look at the details many of these sites have an existing use such as education or community facility. Many are tiny sites that will be devilishly difficult and expensive to develop. I doubt that they could provide more than 40,000 homes at best.

Zac Goldsmith says, “There is no shortage of land…There are 3,500 (housing) estates in the capital: if only a fraction were redeveloped to produce low-rise, high-density streetscapes we would generate enough new housing to cater for our needs for many years.” This is not only vague but misleading. Yes, London needs to increase its densities but this is something that will take generations to achieve and the record of many recent regeneration schemes is not encouraging. The much-vaunted Packington estate has taken well over a decade from start to finish and was conceived under a much more favourable funding regime. At last Sunday’s Housing Bill march, there were hundreds of campaigners from dozens of individual estates where residents are unhappy about regeneration. Progress on estate regeneration is slow and likely to get slower.

All in all, estimates of the amount of brownfield land in London appear to be wildly optimistic.

Selective growth into the green belt is the only realistic solution. A staggering 22% of the GLA area is green belt. Havering and Bromley are more than 50% green belt. A huge amount of this protected land has no amenity or aesthetic value. Much of it is devoted to pony paddocks, golf courses, scrap yards and intensive agriculture with little or no public access. It hems Londoners in and provides little public benefit. Selective development could build hundreds of thousands of homes and create high quality country parks and green lungs that would allow Londoners greater access to the countryside. A report last year suggested that building on just 3.75 of the London green belt around existing transport hubs could provide a million homes.

Khan and Goldsmith assume that Londoners, or at least the ones who could swing the election, want to protect the green belt yet a recent survey by the Campaign to Protect Rural England (of all people) found that more than 50% of private renters and more than 40% of Londoners had never even heard of the green belt! The argument is there to be won.

Turning such an important issue into a game of political name-calling, as Dave Hill highlights here, is simply not good enough. Goldmsith and Khan are misleading Londoners about the capital’s ability to house itself within its existing footprint. You can understand it from Goldsmith, who relies on outer London votes, but Khan should have the courage to make the case for growth in the green belt and take priced-out Londoners with him. His programme is titled ‘A Manifesto for all Londoners’. I would beg to differ. It puts the views of a minority before the needs of the many and lacks vision and leadership.

(This article first appeared in Inside Housing on 15th March 2016)