A coalition of charities have urged the government to reconsider changes to disability living allowance (DLA), saying that proposed reforms could force hundreds of thousands of disabled people into poverty as peers prepare to debate the issue in the Lords again on Tuesday afternoon.

In a joint letter charities including Disability Rights UK, Rethink and and the National Autistic Society warned the cuts could “increase the burden on the NHS and social care system in the long run.”

The government plan to reduce the costs of DLA by 20% and replace it with a new benefit for the ill, the personal independence payment.

On Tuesday morning minister for disabled people Maria Miller defended the government saying: “We have to make sure the money that is there is getting through to the people who need it most. At the moment with DLA we know that isn’t the case.”

But she was challenged by crossbench peer and the president of Disability Alliance Lord Low who told BBC Radio 4’s Today programme: “Disabled people don’t have confidence that the government is yet ready to deliver an assessment system which will achieve an outcome which is fair to them, and takes proper account of disabled people’s needs.”

Welfare reform, which the government suffered three unexpected defeats on last week in the Lords, is a contentious issue for the government.

Disabled athelete and cross bench peer Baroness Grey-Thompson has tabled an amendment, to be voted on on Tuesday, which would force the government to pilot changes to DLA.

A report into the reforms released by a disability rights group has revealed even Boris Johnson had submitted evidence warning the cuts could hurt disabled people.

A spokesman for the Department for Work and Pensions said: "DLA is an outdated benefit and we now have a situation where there are £630 million of overpayments and 71% of people get the benefit for life without systematic checks to see if their condition has changed.

"We are introducing the Personal Independence Payment with a new face-to-face assessment and regular reviews - something missing under the current system.

"Under PIP, support will be focused on those who need it most, with a greater proportion getting the higher rates compared to DLA."

Yesterday the government announced it would not increase the qualifying period for a PIP to six months.