A disabled woman is taking work and pensions secretary David Gauke to court over “unfair and discriminatory” changes that were made to a disability benefit.

There was widespread anger earlier this year when Penny Mordaunt, minister for disabled people, announced new rules that made it harder for people in mental distress to secure mobility support through personal independence payment (PIP).

She brought in the changes after a tribunal had ruled against the Department for Work and Pensions (DWP) and said PIP claimants who need to be accompanied on journeys because of the risk of experiencing overwhelming mental distress could be scored in their assessment in the same way as those who cannot navigate a journey because of a visual or cognitive impairment.

But Mordaunt decided to overturn the tribunal’s decision by changing the rules and tightening eligibility for PIP.

The government’s own figures showed the move to tighten eligibility would see an estimated 164,000 claimants either lose all their eligibility for the PIP mobility component or see it reduced, cutting billions of pounds in spending over five years.

Now one of the PIP claimants affected by the changes is taking legal action against work and pensions secretary David Gauke (pictured).

Lawyers for RF, whose name is not being released because of an anonymity order, are arguing that the changes are “discriminatory and unfair and should not have been implemented without undertaking a thorough consultation”.

She is being represented by solicitors from The Public Law Project, and supported by disability organisations including Inclusion London, Disability Rights UK (DR UK) and The National Autistic Society.

RF’s case will be heard in the high court on 12 and 13 December.

Sara Lomri, RF’s solicitor and PLP’s deputy legal director, said her client had “significant mental health difficulties” and was “bringing this important challenge as the new rules will have a significant negative impact on not only her life, but on the lives of many with ‘invisible’ disabilities.

“She has told me that losing enhanced PIP for mobility means she will not be able to get the support she needs to travel.

“This will have a huge impact on her ability to participate in society.

“My client does not understand why people with mental health problems are being singled out and excluded from a benefit which is supposed to help them.”

Svetlana Kotova, Disability Justice Project co-ordinator at Inclusion London, said: “We have always believed that these changes are discriminatory and unfair and should have never been introduced.

“The DWP introduced them in a rush to reverse [a decision by] the upper tribunal and to prevent thousands of people who need this support from receiving higher awards of PIP.

“They have done this when thousands upon thousands of disabled people are losing their benefits already.

“We have to remember that this challenge is taken in a context when the UN Committee on the Rights of Persons with disabilities found systematic and grave violations of disabled people’s rights a year ago.

“And again, in August, it called the situation disabled people are in a ‘human catastrophe’.

“The UN specifically called on the government to repeal changes to PIP regulations because they breach our human rights under the convention.”

Linda Burnip, co-founder of Disabled People Against Cuts, said the government’s decision to change regulations rather than accept the tribunal’s ruling had been “underhand”.

She said: “This is a particularly important case in relation to entitlement for PIP for people with a mental health condition.

“It is also important to challenge the underhand way in which these changes were introduced by Penny Mordaunt.”

Kamran Mallick, DR UK’s chief executive, said: “When PIP was introduced the government gave a firm commitment that it would take fairer account of the impact of mental health conditions than disability living allowance did.

“However, in practice, the DWP did not award the PIP mobility component to those who are unable to plan or undertake a journey due to ‘overwhelming psychological distress’.

“This resulted in a successful and welcome legal challenge holding that PIP did in fact allow for such awards.

“But instead of accepting this judgment, in March 2017 the Government changed PIP rules to exclude those with severe mental health problems.

“Many people that experience conditions like anxiety, agoraphobia, schizophrenia, and post-traumatic stress disorder, struggle to make journeys because of psychological distress.

“They face similar costs to those with a physical disability – for example needing to use taxis or hiring a support worker.

“The PIP rule changes were implemented without consultation and we are in no doubt that they are clearly discriminatory and unfair.

“Just a few months ago, the United Nations found in a damning report that UK legislation has ‘failed to recognise living independently and being included in the community as a human right’.

“If the government is serious about delivering a fair and equal society it should reverse the changes to PIP so that those with poor mental health are not treated like second-class citizens.

“Until then, we strongly support the high court case brought by the Public Law Project and hope its success moves the government to change the rules.”

A DWP spokeswoman said: “We cannot comment on an ongoing legal case.”

But she referred Disability News Service to statements issued earlier this year.

In a statement to MPs in February, Mordaunt said the tribunal judgement had “broadened the way the PIP assessment criteria should be interpreted, going beyond the original intention” and that the government’s changes would “provide greater clarity”.

She also spoke of the “implications [for] public expenditure” of the judgement.

An equality analysis published by DWP in February showed the judgement would have cost an extra £900 million a year by 2021-22 if the regulations had not been brought in.