LONDON - A third of Britain is effectively off-limits to lower-income working families because private rents are unaffordable, a new report claims.The report comes from the Resolution Foundation, which campaigns on behalf of low to middle-income families.It says most of southern England is now beyond the reach of less affluent households.The housing minister said the report was ‘factually flawed’ and failed to take housing benefit into account.With social housing usually unavailable and home ownership unaffordable for many first-time buyers, renting privately is often the only option for households on lower incomes.A BBC ‘housing calculator’ also identifies how renting a modest two-bedroom home for less than £700 a month is almost impossible in London and much of the South East. Modest is defined as having a rent below 75 per cent of similar properties in the area.The Home Truths report identifies local authorities that are ‘affordable’ for a couple with a child requiring a two-bedroom property on a household income of £22,000 a year. Affordable is defined as a rent that is no more than 35 per cent of net household income.On that basis, 125 of 376 local authorities in Britain (33 per cent) are unaffordable for less-affluent working families."The private rented sector is now, in large parts of the country, the most expensive form of housing,” said Vidhya Alakeson of the Resolution Foundation."It is also the only option for most low to middle-income households, many of whom are faced with the unenviable choice of forgoing other essentials in order to pay for housing or living in overcrowded conditions to reduce their housing costs.”Housing Minister Mark Prisk described the report as ‘alarmist’ as it "suggests rents are soaring when in fact they have fallen in real terms”."And it fails to recognise that housing benefit provides a safety net which ensures that up to a third of private properties in most areas are affordable to low income families,” he said.