Large swaths of southern England will become off limits to housing benefit recipients in a little more than a decade because of the government's proposed plans to cut welfare bills – triggering a huge migration of the poor to the north – according to a study by housing experts.

The work, by the Chartered Institute of Housing, shows that before 2025 rents on most two-bedroom properties in the south will become unaffordable to those claiming local housing allowance.

Within 15 years, much of London's commuter belt will become too expensive for the state to pay for the poor to live in. Towns such as Chelmsford, Newbury, Bath and Maidstone would be no-go areas for those on benefits and all of Hertfordshire would be out of bounds. The capital would be unaffordable within a decade.

The findings reinforce concerns expressed today by Rowan Williams, the archbishop of Canterbury. Williams attacked the government's welfare plans, saying he was particularly concerned about the cuts in housing benefit.

"My worry there is that people's housing is part of their sense of stability, part of their sense of having a secure future, and I'm also a bit worried about the way in which this could lead to a kind of social zoning, where middle-class areas get more solidly middle class and other people are pushed out to the edge," he said in an interview with the BBC.

Williams also said he had "a lot of worries" about the government's plans, due to be spelled out this week, to force the long-term unemployed to do four weeks of unpaid work. He said: "People who are struggling to find work and struggling to find a secure future are, I think, driven further into a downward spiral of uncertainty, even despair, when the pressure is on in that way."

Before a parliamentary debate on the proposed changes to housing benefit, campaigners argue the debate has focused too much on the capital and the possible effect of "cleansing" its centre of the poor. This has eclipsed the bigger cuts affecting families up and down the country.

Sam Lister, head of policy at the housing institute, said the result would see the poor forced out of their homes, from "where the jobs are in the south to where there are far fewer [jobs] in the north".

The changes aim to force benefit recipients to rely on income rather than the state to meet housing needs. However, Lister said the "perhaps unintended consequences" of relocating thousands would undermine any idea that welfare reform will make it easier to find work.

"Basically if you draw a line from the Wash [in East Anglia] to the Severn [at the Bristol Channel] that would be a southern England in 10-15 years where rents are simply unaffordable [for] those living on housing benefits. You then get people forced to move from where the jobs are to where there are far fewer.

"It's making worklessness worse. It's not relieving it."

The findings show starkly how the three main reforms suggested by the government combine to sharply limit the amount of housing available to the poor.

Because rents rise at an average of 5% a year, the government ceiling of £250 a week housing benefit for a two-bedroom home would be quickly reached in many parts of the south. This is exacerbated by the allowances being scaled back by pegging them to the bottom third of rents in any borough and increasing the subsidies only in line with consumer price inflation.

"The government keeps saying that landlords will drop their rents, but there is no evidence for that," said Lister. "What we will see is the south of the country becoming just unaffordable and people forced to move out so far it becomes impossible to travel in to areas where there is work."

Karen Buck, shadow minister for work and pensions, said that the work echoed a study by Cambridge University in September that showed by 2018 only 5% of two-bedroom dwellings will remain affordable to those claiming housing benefit in Manchester. "This shows the share of properties available to those on housing allowance shrinks far faster than the government wants you to believe. Ten of thousands of households will experience real pain."

A spokesperson for the Department for Work and Pensions said tonight that it was trying to deal with the "problem now, not in 10 years' time or in the future". "For example, no one predicted the 80% growth in housing benefit over the last decade. We want to deal with today's issues."

She added that it was the government's plan not to concentrate jobs in the south and that people would be able to move to find work in other parts of the country. "This is why it is important to invest in the economy and grow jobs across the UK."

The department also released figures showing that private rents fell by 5% between November 2008 and February 2010, while housing benefit rents went up by 3%. "It is clear that housing benefit rents are rising faster than the market," said the welfare minister, Lord Freud. "Private sector landlords are taking advantage of a system that's clearly out of control."

Charities are also warning of the dramatic impact on livelihoods of the cuts. Shelter, the housing charity, today produced research showing that almost a third of councils outside the capital will have households facing losses of more than £50 a month following the cuts.

Almost 780,000 people outside London who receive local housing allowance in the private rented sector will lose out.

Of 283 local authorities outside the capital, 81 will see two-bedroom households in their area lose an average of £50 or more, while 156 will see households losing an average of more than £30 a month when the rate at which local housing allowance is paid is cut from October next year.

The impact will be felt in every region across the country. In Manchester recipients will lose £61 a month, while in the north-east households in Newcastle will see a drop of £43.

Some of the worst hit live in the south-east. The loss in Cambridge is estimated at £100 a month, while those in Brighton and Hove and Woking will lose £69.

Shelter's chief executive, Campbell Robb, said such losses represent "huge amounts" to some of the poorest people in Britain.

"Imagine if you are on jobseeker's allowance of just £65 a week or a pensioner surviving on £98 a week, or those on the minimum wage of £218 a week. These losses represent a significant proportion of their income. They will really struggle to find the extra money they will need to keep a roof over their head."

"The focus of debate so far has been the cap to housing benefit and the impact on London, but this analysis shows that these cuts will affect hundreds of thousands of people across the country."

Tomorrow, MPs will vote on the housing benefit changes in a debate staged by Labour. Several Lib Dems have spoken out about the plans, but most are not expected to vote with Labour because they are critical of its record on housing.