George Osborne has "declared war on the disabled" by slashing benefits, Jeremy Corbyn said as a Conservative campaigner closed down a party-linked website in protest.
The Budget confirmed that £1.3 billion of £4.2 billion annual cuts due by 2020/21 would come from reductions to personal independence payments for disabled people.
Mr Corbyn said Labour would "fight to overturn these callous cuts" with the Chancellor also braced for a backlash from some of his own backbenchers.
Opposition to the move was illustrated by the decision of lifelong Tory voter Graeme Ellis to quit the party and make his views clear on the official site of the Conservative Disability Group, on whose executive he has served.
"This website is temporarily closed owing to Disability Cuts," a message read after Mr Osborne confirmed the cuts.
"The owner of the hosting package, Graeme Ellis, has resigned over disability cuts from the group and will no longer develop or host this site."
Mr Ellis, a former NHS worker who has diabetes and uses a wheelchair, said the Chancellor was "destroying lives".
"I've been a Conservative voter since I could vote. But as a lifelong Conservative I could no longer agree with what the Government's doing," he told the Mirror.
"How can I morally represent clients when I remain in an organisation that's doing these cuts?"
A Conservative Party spokesman said: "The Conservative Disability Group has not deactivated its website.
"The owner of the domain, who is no longer a member of the group, has deactivated it without any instruction to do so."