Suburbia, depending how you measure it, is where most people live. It is the most pervasive urban invention of modern times, one in which Britain played a leading role.

Often, it stays under the radar of urban theorists and policymakers. But it is emerging as a major untapped resource and, therefore, a battleground in the struggle to find somewhere, anywhere, to put new housing. Last week, the mayor, Sadiq Khan, revealed his draft for the new London Plan, the document that will guide the planning decisions of the city’s boroughs. He wants – and who wouldn’t? – more housing, more of it affordable, well designed and energy-efficient, complete with spaces that encourage walking, cycling and the use of public transport. He has limited powers – he can’t, for example, ordain the large-scale public housing programmes that even the estate agents Savills now thinks are necessary – but he can manipulate the planning system to promote some kinds of development over others.

His eyes alighted on the suburbs. Between the First and Second World Wars, while London’s population increased by 17%, its land area doubled, a reflection of its rapid suburban expansion at a much lower density than its historic centre. In theory, this means that if suburban densities could be nudged up, very many more homes could be accommodated within London’s boundaries. As Professor Tony Travers, of the London School of Economics, says, Greater London could house 20 million people if it was all built to the same density as the inner borough of Islington.

So Khan wants to encourage, within 800 metres of transport links, developments that provide more housing in the same space. In doing so, he hopes to encourage smaller-scale developers and lower-cost housing, in contrast to the luxury towers promoted by his predecessor, Boris Johnson, in the name of meeting housing needs. This might mean building on gardens or building at four storeys instead of two.

He has, say Tory opponents, “declared war on the suburbs” and will make them “overcrowded and harder to get around”. Yet making suburbs denser could make them better. In principle, having more inhabitants means more life in town centres and high streets, which makes shops and businesses more viable and makes it easier to sustain such things as local bus services.

As the architects HTA suggested with proposals called “Supurbia”, it could make for more pleasant and safer streets than the sparsely populated, car-dominated thoroughfares that tend to occur in suburbs. It’s a reasonable fear that suburbs might lose their essential greenness, but a look at the maps in the draft plan shows that the great majority of outer London would fall outside Khan’s 800-metre circles.

In principle, making some parts of suburbs a little more like Islington, whose desirability is reflected in astronomic property prices, shouldn’t be a bad thing. It depends completely on how it’s done and here we have to hope that Khan’s promises on design, affordability and enhanced public spaces come true. Because the enhancement of the suburbs could be good for pretty much everyone and it’s too good an opportunity to waste.