In a move that could be a huge boost for the construction industry, the Conservatives are promising first time buyers under the age of 40 20% off a new home if they are re-elected.

The party estimates there would be around 100,000 new houses built on brownfield sites because of the policy by excluding homes built under the Help to Buy Starter Homes scheme being exempt from a range of taxes allowing them to be sold at a considerable discount on their market value.

The government has also told developers the requirements to build social housing would be waived as part of any development and the zero carbon homes standard, applicable from 2016, would also be exempted.

Of the policy, David Cameron commented: “We want to help more young people achieve the dream of home ownership so today I can pledge we will build 100,000 homes for young, first-time buyers. We will make these starter homes 20 per cent cheaper by exempting them from a raft of taxes and by using brownfield land.

‘I don’t want to see young people locked out of home ownership. We've already started to tackle the problem with Help to Buy mortgages, and these plans will help tens of thousands more people to buy their first home.”

This announcement follows on from one made by Communities Secretary Eric Pickles, in which a programme of loans of £400m would be made available to housing associations and developers to assist in the building of 10,000 new homes.

The properties built in the buy to rent scheme would have a rental cap of 80% of market value for a period of seven years after which the occupants will be given the chance to buy the properties.

Loans for the buy to rent scheme will be split 50:50 between London and the rest of England (it will be known as the London Housing Bank in London).

London Mayor, Boris Johnson said: “We hope to provide thousands of brand new homes many years sooner than would otherwise be possible.”