The head of Theresa May's policy unit has been urged to apologise and was accused of dragging the Tories into "the gutter" after defending changes to disability benefits.

George Freeman suggested personal independence payments (PIP) should go to "the really disabled people who need it" rather than those who are "taking pills at home, who suffer from anxiety".

He defended Government reforms to PIP, saying they were needed to roll back the "bizarre" decision of a tribunal, which said claimants with psychological problems who cannot travel without help must be treated like those who are blind.

The tribunal also said claimants who need support to take medication should be assessed the same way as those managing therapies such as dialysis at home.

Responding to the upper tribunal rulings on Thursday as Westminster's attention was on two by-elections, disabilities minister Penny Mordaunt said she was reforming the payments to "restore the original aim of the benefit" to make sure the most needy were given support.

Ms Mordaunt said no claimants would see a reduction in the amount of PIP previously awarded.

But Labour said the Government's equality assessment showed 160,000 would miss out on money that was "rightfully" theirs.

Mr Freeman, the head of the Number 10 Downing Street policy board, said it was the right decision.

He told Pienaar's Politics on BBC Radio 5 Live: "These tweaks are actually about rolling back some bizarre decisions by tribunals that now mean benefits are being given to people who are taking pills at home, who suffer from anxiety.

"We want to make sure we get the money to the really disabled people who need it."

Challenged on his assessment of anxiety, Mr Freeman said: "I totally understand anxiety and so does the Prime Minister. We've set out in the mental health strategy how seriously we take it.

"My point was that these PIP reforms are partly about rolling back some frankly bizarre decisions in tribunals which have seen money that should go to the most disabled spent on people with really much less urgent conditions."

Shadow chancellor John McDonnell tweeted: "This is an insult to disabled people. (George Freeman) should apologise immediately or Theresa May should make him."

In a separate statement, he said Labour would push Chancellor Philip Hammond to reverse the changes in next month's Budget, arguing they amount to a £3.7 billion cut to disability benefits.

Mr McDonnell said: "Theresa May has used the cover of the by-elections to sneak out this announcement hurting so many vulnerable disabled people.

"This is a return to the worst politics of spin that so tarnished our politics for so long. It is an act of immense bad faith. She is degrading politics and demeaning the role of Prime Minister."

Reacting to Mr Freeman's comments, Labour MP Louise Haigh tweeted: "They know this will affect ppl w/ PTSD, dementia, schizophrenia, seizures.

"Tories in the gutter trying to shame those in desperate need".

Tory MP David Burrowes, who rebelled over separate cuts to disability benefits last year, signalled he would back the changes, although he admitted it was a "difficult judgment call" to make about who should receive the highest PIPs.

The Prime Minister has made tackling mental health a priority, saying last month that mental illness has for too long been "shrouded in a completely unacceptable stigma and dangerously disregarded as a secondary issue to physical health".

Disability charity Scope criticised Mr Freeman's "crude" distinction between physical and mental health and said it was concerned about the Government's "worrying" changes to PIP.

Scope chief executive Mark Atkinson said: "It is unhelpful to make crude distinctions between those with physical impairments and mental health issues because the kind of impairment someone has is not a good indicator of the costs they will face.

"Many disabled people will be now be anxiously waiting to hear as to whether or not these tighter rules will affect their current PIP award.

"The Government must offer clarity and reassurance that these new measures will not negatively affect the financial support that disabled people receive now or in the future, and that they stand by their commitment to making no further changes to disability benefits in this Parliament."

The independent Equality and Human Rights Commission said Mr Freeman's comments would add to the stigma surrounding mental health.

Its chief executive Rebecca Hilsenrath said: "Our welfare system should support those that are in need.

"Any decisions should be based on sound evidence and not sweeping generalisations.

"There are many people who have unseen disabilities and they need just as much support.

"These comments will only feed into negative perceptions of disability and add to the stigma surrounding mental health issues."