Some 200,000 homes will be made available to first-time buyers in England by 2020 if the Tories win the election, David Cameron has promised.

The coalition government has already announced plans for 100,000 cut-price homes for people aged under 40.

Mr Cameron said his party would double it if elected, giving more people the security of owning their own home.

Labour said the plan was inadequate and housing groups warned affordable rented schemes would lose out as a result. 

First-time buyers under the age of 40 in England can now register to buy new homes at a discount of up to 20% off the normal price. 

Fees waived

The offer is part of the government's new "starter homes" scheme to encourage home ownership and construction on previously used "brownfield" land. 

The 20% discount will be paid for by waiving the fees homebuilders have to pay to local authorities under so-called Section 106 agreements, amounting to at least £45,000 per dwelling on brownfield sites.

The Conservatives say homes worth £250,000 outside London - or £450,000 in London - would be eligible for the scheme and that first-time buyers would have to repay the 20% price advantage if they sold within five years. 

In a speech in Colchester, Mr Cameron said there was "a particular kind of security that comes with owning your own home" that "too many people have been denied", due to what he described as a "quiet crisis" in affordability.

"The young people in their 20s and 30s still living with their parents, desperately saving for their own place. The couple who want a child but can't afford to upsize - even though they have both got have full-on, full-time jobs. It shouldn't be this way.

"Our goal is a Britain where everyone who works hard can have a home of their own."

'Not shoeboxes'

He said Britain's biggest builders, including Barratt and Taylor Wimpey, had signed up for the expanded scheme and it would be designed so that new properties could not be "snapped up by buy-to-let landlords".