A "significant number" of disabled people living in specially adapted homes have had to bear the cost of the so-called bedroom tax because it is too expensive for them to move, a Labour MP has said.

Dame Anne Begg, chairman of the work and pensions select committee, said the housing benefit bill had not come down because people were now more appropriately accommodated.

She said those who had spent a lot of money making their home suitable for their condition had been forced to subsidise the money lost through the spare room subsidy from other benefits.

Another problem, Dame Anne said, was the lack of smaller housing across the country, even in the private sector.

Speaking in a Commons debate on welfare, she said: " The only option for many people was to remain in the house they were and as a result have their housing benefit reduced. All they could do was make up the shortfall in other ways."

Her committee has recommended exempting those in adapted homes from the subsidy, but the Government argues protection is available through discretionary housing payments (DHPs)

Dame Anne stressed their discretionary and temporary nature, pointing out that local authorities can set their own eligibility criteria.

If they are to be used in the long term, she said, more funding was needed, adding that it was to be cut from £165 million this financial year to £125 million in the next.

The Labour MP also called for revised guidelines to be distributed to councils telling them to exclude disability benefits from means testing for the DHP.

She used the start of her speech to criticise the Government for not yet responding to her committee's report, which was published in April last year.

DHPs are funded by the Government to help people who cannot move to avoid the charge and who need the extra bedroom.

The spare room subsidy or bedroom tax has been a long-running sore between the Government and Labour. It deducts money from housing benefit where a household has more bedrooms than residents, with some exemptions.

Labour has pledged to repeal the measure if it wins in May.

Liberal Democrat John Hemming (Birmingham Yardley) encouraged young people on benefits who could be hit by the bedroom tax to rent out their spare rooms.

Doing so would avoid having to pay the tax and they would also be able to keep up to £20 a week of additional money, he said.

Mr Hemming told MPs: "One of the changes which was brought in in April 2013 was to enable people in the socially rented sector to benefit in the same way as those who own their own homes if they wanted to let out the room to a lodger or boarder for instance.

"So they can actually not have to pay for the spare room because it's occupied but also keep up to £20 a week of the additional money.

"Now given that the applicable amount for somebody aged 25 at the moment is around about £71.70, £20 a week is quite a lot of money.

"My belief is only a handful of people in Birmingham have taken that up but I think that's a lot because people don't know that they can benefit.

"I had a meeting last night with care leavers when we looked at the issue of housing, housing is absolutely critical.

"We were discussing the fact that it is really quite tight living on means tested benefits because you have to pay the water bill, the gas bill, the electric bill.

"There are great merits in people sharing property in certain circumstances and I advised young people there to be looking, rather than trying to live alone, to share."

Conservative Chris Heaton-Harris (Daventry) said: "It has been fairly obvious that different parts of the country and different housing associations and different councils have acted in completely different ways over this.

"Probably in their best local interest, and that's fine, but that has led to different outcomes in various parts of the country. They all have remarkably significant different pressures on them.

"The pressures on housing in Erith and Thamesmead or Barking and Dagenham I completely acknowledge are completely different to those that happen in my constituency."

Replying to the debate for Labour, Helen Goodman said: "The Government set itself three targets for its welfare reform programme and changes to housing benefit - reducing benefit expenditure, improving incentives to work and making the situation fairer.

"It is quite clear the first test has been failed. The OBR shows expenditure in 2009/10 on housing benefit was £20 billion. In 2013/14, the last year for which we have full statistics, £24 billion. The OBR is predicting by 2018/19, the spend will be £27 billion.

"The problem with this Government's policy is it has made life more difficult for many people but still the benefits bill continues to rise... it is because the Government has still not tackled the underlying issues.

"The OBR shows while housing benefit to unemployed people has fallen and is projected to continue to fall, housing benefit to those in work is rising steadily between 2012 and 2019.

"This... demonstrates the new poverty is in work poverty."

Minister of State for Disabled People Mark Harper defended the Government's record.

He said: "I think our policies are working, they've driven the lowest rise in the welfare bill since the creation of the welfare state and they are also helping to get people back into work, which is why we see a record number of men and women across the country in work, demonstrating that success of a long term economic plan."