A final attempt to halt controversial curbs to disability benefits will be made tomorrow, after MPs were granted an emergency debate.

Ministers will be accused of a “troubling subversion of democracy” after sneaking through the changes to Personal Independence Payments (PIPs), hitting the mentally ill.

Ministers refused to allow a vote on ‘emergency legislation’ to tighten the criteria for PIPs, overturning a tribunal ruling that they should also cover conditions including epilepsy, diabetes and dementia.

Anger grew when it emerged the Government’s own welfare experts had called for a delay until the changes had been properly tested and “clearly understood”.

It was “not clear” how assessors would interpret the changes – raising the danger that claimants would not be “consistently treated”, the Social Security Advisory Committee (SSAC) warned.

On Monday night, the Government was defeated in the House of Lords over the controversy on a Labour motion “regretting” the changes and demanding a review of their impact on people with mental health conditions.

Now MPs will finally get to put the Department for Work and Pensions (DWP) on the spot, after John Bercow, the Speaker, granted the 90-minute debate.

The overturning of two tribunal judgments is expected to deny the higher rate of PIP to more than 160,000 disabled and chronically sick people.

The people most affected include those with autism or schizophrenia, along with those suffering the effects of dementia or stroke, according to the Government’s own analysis.

Debbie Abrahams, Labour’s Work and Pensions spokeswoman, will strongly criticise the DWP’s use of emergency legislation – thereby bypassing its own welfare advisors.

And she will accuse ministers of deliberately seeking to prevent a vote until it was too late to stop the changes, a deadline that passes next Monday.

“These regulations were laid down without any consultation with the Social Security Advisory Committee and, despite repeated efforts, without any debate in this chamber,” Ms Abrahams will say.

“By delaying the debate, the Government is hoping that the objection to these regulations will be kicked into the long grass.

“I believe that we owe it to those who will be affected, primarily people with mental health conditions, to hold this Government to account.

Last month, Damian Green, the Work and Pensions Secretary, refused to allow MPs to vote on the changes – insisting that was “above my pay grade”.

Significantly, Mr Green also acknowledged “a handful of people” could now have their PIP payments cut, having been awarded higher sums since the tribunal’s rulings.

The admission appeared to contradict repeated assurances – including by Theresa May – that no disabled people would lose money, with only new claimants affected.

Ministers say failing to overturn the ruling would divert £3.7bn over the next five years from more severely disabled people, but the SSAC disputed that figure.