Private rents are now unaffordable in 55% of local authorities in England, the housing charity Shelter has said.Homes in these areas cost more than 35% of median average local take-home pay - the level considered unaffordable by Shelter's Private Rent Watch report.The charity said 38% of families with children who rent privately have cut back on buying food to help pay rent.Housing Minister Grant Shapps said it had curbed red tape "which would have pushed up rents and reduced choice".Shelter's research found rents had risen at one-and-a-half times the rate of incomes in the 10 years up to 2007.'Dramatic impact'It said private rents in 8% of England's local authorities were "extremely unaffordable" - with average rents costing at least half of full-time take-home pay.Just 12% of areas were affordable, it added.Shelter analysed two-bedroom homes because they were so widely found and used Valuation Office Agency and Office for National Statistics data.Chief executive Campbell Robb said: "We have become depressingly familiar with first-time buyers being priced out of the housing market, but the impact of unaffordable rents is more dramatic."With no cheaper alternative, ordinary people are forced to cut their spending on essentials like food and heating, or uproot and move away from jobs, schools and families."Rural areas were found to be worst hit by the high rentals relative to income, with rents in Manchester and Birmingham more affordable than in north Devon or Herefordshire.Alice Barnard from the Countryside Alliance urged the government to "urgently review" the rental market in rural areas.Housing Minister Grant Shapps said the government recognised the importance of private landlords in providing accessible and affordable homes."We have stopped the imposition of excessive new red tape on the private rented sector, which would have pushed up rents and reduced choice for tenants," he said."We also need to build more homes given new house building fell to its lowest peacetime levels since the 1920s under the last administration."He said councils would be rewarded for freeing up disused public land to build on.