Shelter has said there are only 43 homes on the market in London which are affordable for first-time buyers.

The figure would have been even lower had the calculation not included four houseboats and one mobile home.

The organisation says that across England, just one in five homes currently for sale are affordable, and that in 35 local authorities there is not one home currently on the market that a typical young family could afford to buy.

Shelter did its research by looking at listings on Zoopla with two or more bedrooms.

Using data from the Council of Mortgage Lenders, it assumed that its typical young family were aged 23 to 29 with one or two children, with one part-time and one full-time earner. They had a 17% deposit and could get a mortgage of 3.4 times income. According to the latest Annual Survey of Hours and Earnings, the median income for a family of this type is £30,748.

In total, Shelter found 42,185 two-bedroom homes across England on Zoopla that were affordable.

The north-east was the most affordable, with 42% of homes within reach of a young family buying for the first time.

Campbell Robb, chief executive of Shelter, blamed the severe lack of affordable housing on a failure to build new homes.

“It’s no wonder that a week out from election day, affordable housing is a key concern for those heading to the polling booths.

“For the next government, whoever that may be, it’s time for the talk to stop and the work to begin.

“Politicians need to act swiftly to deliver the plan that will build the 250,000 homes a year we need, or millions more people will be forced to kiss their dreams of a stable and affordable place to live goodbye.”