The head of Theresa May's policy unit has said he regrets "any offence" caused by comments in which he appeared to indicate people suffering anxiety were not "really disabled".
George Freeman said he had personal experience of the problem and knew "all too well" the pain caused by anxiety and depression.
The Tory MP had come under fire after suggesting 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".
In response to the storm around his comments, Mr Freeman said on Twitter: "Having experienced myself traumatic anxiety as a child carer living w alcohol I know all too well the pain anxiety + depression causes, which is why as a former health minister and policy adviser I am passionate about supporting mental health and disability, and hugely regret if my comment about the need to prioritise the most 'serious disabilities' inadvertently caused any offence which was not intended."
Mr Freeman's comments came as ministers faced backbench Tory pressure to reverse the plans to roll back a legal ruling extending the disability benefit.
Tory MP Heidi Allen urged disabilities minister Penny Mordaunt not to go ahead with plans to roll back a legal ruling extending the key disability benefit, telling her: "Don't do it."
She called for a top-to-bottom review of the PIP system, which she said was "not fit for purpose".
Ms Mordaunt has said she will take action to ensure PIPs go only to the most needy, after a tribunal ruled claimants with psychological problems who cannot travel without help must be treated like those who are blind.
South Cambridgeshire MP Ms Allen said the judgment on whether an individual's disability was bad enough to entitle them to benefits should be taken on a "person-by-person basis" and was not one for MPs to make.
Ms Allen said the Government should think again about the decision, expected to affect 160,000 people and save £3.5 billion in future years.
She told the BBC Radio 4 Today programme she believed other Tory backbenchers would share her view.
"In my view, the courts are there for a reason," said Ms Allen.
"If they have come up with this ruling, which says that the criteria should be extended, then I believe we have a duty to honour that. That is their role.
"Does that mean we should look at the process as a whole? Frankly I think we should do that anyway. It is not fit for purpose at the moment."
Ms Allen suggested Mr Freeman may not have been "fully aware of the detail" of the ruling when he made his comments.
The tribunal called for payments to go to those with "overwhelming physical distress", which sounded as though it referred to those with a "severe mental health problem" and not simply a bit of discomfort, she said.
Ms Allen said the Government had a "really bumpy year" in 2016 because of proposed cuts to another disability benefit, Employment and Support Allowance, which she still hoped would be reversed in next month's Budget.
Asked for her message to Ms Mordaunt, the MP said: "Don't do it. If I was in her shoes, I would take the financial hit and say we need to accept this.
"Now let's really look at this PIP policy, which is something that needs to happen anyway, and review the whole thing from top to bottom."