The Conservatives will lose the next election because of the growth of generation rent. If it is to stand any chance of winning, it must reverse falling levels of home ownership.

The warning has come from think tank Onward, run by Will Tanner, a former deputy head of policy to Theresa May.

In new analysis due to be published today, Onward will say that the number of private renters is increasing faster in marginal seats that the Tories must win in order to gain a majority, than in safe Tory-held constituencies.

Onward says that the prospect of owning a home “is becoming a pipe dream for a generation”. It calls for “very radical action to get home ownership growing again”.

The analysis, by MP Neil O’Brien, cites research showing that private tenants are likely to vote Labour, while home owners are more likely to vote Tory.

The number of constituencies in which private renters make up more than one-fifth of households is set to reach 253 by the 2022 election – up from 18 constituencies in 2001.

In the 20 most marginal seats, the proportion of households in private rented accommodation is due to rise 3% by 2022, to average 21.8%. In the 20 safest Tory constituencies, 15.5% of households will be renting privately.

The marginal seats that the Tories will need to target are scattered and include Kensington, Labour majority of 20; Perth and North Perthshire, SNP majority of 21; Dudley North, Labour majority of 22;  Newcastle-under-Lyme, Labour majority of 30; Crewe and Nantwich, Labour majority of 48; and Canterbury, Labour majority of 187.

Separately, in an interview with the Sunday Telegraph, government housing adviser Sir Oliver Letwin has called for a huge shake-up across the whole housing and infrastructure industry to speed up delivery of new homes.

He said it is taking developers 15.5 years to complete large schemes and also called for thousands more bricklayers.

The newspaper ran it as its lead story yesterday under the headline ‘War spirit needed to fix housing shortage’.