The report said the houses could be built on derelict land which is currently being used for garages and sheds.
And the Conservatives have called for “urgent” action from councils to ensure that the land is comprehensively surveyed to identify sites on housing blocks and estates that would be suitable for infill homes.
Report author Steve O’Connell said: “We need an urgent, mass scale, coordinated effort to turn the thousands of redundant spaces in blocks and estates into housing.
“A huge part of this is encouraging people to build their own homes. Some quick research for my report shows that it’s possible to build a well-insulated, energy efficient home for less than 50k.
"The opportunity to build homes on a shoestring budget will help the likes of young professionals and first time buyers who may otherwise struggle with hefty deposits.”
O’Connell said that self-builders need the land highlighted in the report to build on and called on Mayor of London Boris Johnson to give the first of the plots to such builders.
He said: “I have identified over 4,000 disused sites and spaces across just 13 boroughs of London, and I’m urging the Mayor of London to initially pilot self-building on 100 of these spaces.
“My action plan also involves every borough identifying their disused sites and spaces, putting them into their next available housing delivery plan, and getting the Mayor to scrutinise them.
“If all boroughs fully explore this potential we could deliver at least 10,000 homes in 10 years. Let’s get started.”
The report also called on the Mayor to amend the London Plan to require all London boroughs to review the potential to create new homes on small sites on existing housing estates.
