Nearly 50,000 new homes will be built in 2013, Nick Clegg pledges

Nearly 50,000 homes could start being built next year as a result of the government intervening to unblock stalled projects. In a preview of next month's autumn statement by the chancellor, Nick Clegg will outline on Thursday the plans in a speech warning of a housing crisis in which more than 100,000 new homes are needed.

Housing groups and business leaders have also been calling for a boost in housebuilding, which would quickly create jobs and stimulate growth in the UK's stagnant economy.

The Lib Dem leader will also detail the government's plans for a competition to build new "garden cities and suburbs", modelled on the more ambitious new towns such as Letchworth and Welwyn, built in the early 20th century, and Corby, Basildon and Milton Keynes, created after the second world war.

"Unless we take radical action we will see more and more small communities wither, our big cities will become every more congested as we continue to pile on top of each other and the lack of supply will push prices and rents so high that – unless you or your parents are very rich – for so many young people living in your dream home is going to be a pipe dream," the draft of Clegg's speech says. "There's only one way out of this housing crisis: we have to build our way out."

Clegg's speech follows a host of government announcements that have promised to "kickstart" the house building industry, including a major housing strategy announced a year ago with the promise that it would be "ambitious" and "deliver homes and strengthen the economy"; an independent review of the problems led by the chairman of 3i investment group, Sir Adrian Montague, which reported earlier this year; and an ongoing review of house building standards intended to cut red tape for builders.

Statistics released last week show that in the 12 months to the end of September, new housing starts fell 9% to less than 100,000, though completions rose by 6% to 117,190.

The government is also competing with half a century of under-building of new homes, and the failure of the Labour government's ambitious "eco-towns" project which, similar to the coalition's new towns programme, had intended to construct new settlements of up to 20,000 homes.

Clegg will argue that the "politics of housebuilding is shifting" as parents are increasingly worried about how their children will get on to the housing ladder – potentially counterbalancing a long history of local opposition to new developments. The average age at which people can now afford their first home has risen to 35.

"As we, as a society, become more open to development that creates the space for politicians to be bold," say extracts of Clegg's speech.

Clegg will announce that the government has found "a number of large locally-led schemes" – of between 4,000 and 9,500 homes – which had "hit a wall" and pledge to "intervene directly", including providing funding in the form of loans which would be repaid when the homes were sold. If all the schemes went ahead, they would build 48,600 new flats and houses, he adds. All were ready to start building new year if they could be helped, said sources close to Cameron.

However the deputy prime minister is set to disappoint housing experts who have called on the government to release public land to speed up new developments by only demanding payment once the homes were built and sold, signalled sources.

The National Housing Federation welcomed the focus on a long-term programme rather than ad-hoc initiatives. Its chief executive, David Orr, said: "But such an ambitious programme shouldn't come at the expense of other shorter-term measures which could deliver growth quicker, for example giving small parcels of public sector land over to developers to be built on."

Jack Dromey MP, Labour's shadow housing minister, said: "On house building the government has made announcement after announcement followed by failure after failure.

"Rather than more empty promises we need the government to take real action now and to tackle the housing crisis and boost our flatlining economy.

"That is why they should back Labour's call to use the windfall from the 4G auction to build 100,000 more affordable homes, and give a stamp duty holiday to first time buyers."