Peers will attempt to delay changes that would deny some people disability benefits after they were attacked by the Government’s own welfare experts.

The fight against changes to Personal Independence Payments (Pips) – which will affect the mentally ill – will continue in the House of Lords, The Independent has learned.

MPs were furious when 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.

That anger grew when it emerged the Government’s 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.

Although the changes came into force last Thursday, a 40-day period for opponents to force a challenge to the regulations does not lapse until 3 April.

Now Labour will attempt to pass a “regret motion” in the Lords which, if successful, would force the Government to produce a report to explain why it is ignoring its own experts.

Baroness Sherlock, the party’s work and pensions spokeswoman, told The Independent: “These regulations overturn two tribunal judgments which would have enabled 164,000 disabled and chronically sick people to apply for the higher rate of Personal Independence Payment.

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

“We will demand ministers put in place a full and proper scrutiny process and support the SSAC's advice to hold talks with health professionals.”

The vote on the motion is likely to take place on 29 March, with a separate Liberal Democrat attempt to force a rethink also mooted that week.

Regret motions rarely force a change in policy – but did succeed both over planned increases in court fees and, most famously, over cuts to tax credits.

In the Commons, 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.

In a letter, Mr Green agreed to ‘further clarify” the policy if necessary, but rejected the warnings about confusion and inconsistent treatment.

“We are confident that health care professionals understand how to assess people effectively even where their conditions impact them in both physical and psychological ways,” the Work and Pensions Secretary wrote.