British Prime Minister, David Cameron, said he is “puzzled and confused” after the surprise resignation of a top cabinet minister in protest to new budget proposals. Iain Duncan Smith, who was Secretary for Work and Pensions, oversaw serious reform to welfare in what the Conservative party espoused as a drive to move people into work.

But Mr. Duncan Smith resigned on Friday with a letter lambasting further cuts to disability, writing a letter to the Prime Minister that branded the latest cuts as “a compromise too far.”

The resignation is a surprising blow to the UK’s Conservative government, since Duncan Smith was instrumental in propelling the new welfare reforms.

Some government officials are reportedly bewildered at the exit, arguing that the move is at odds with his long-standing position on welfare policy.

Duncan Smith’s letter to the Prime Minister was a heavy shot at the Treasury’s latest proposals to slash Personal Independence Payments, a form of welfare paid monthly to the disabled. In his letter, Duncan Smith wrote: “I am incredibly proud of the welfare reforms that the government has delivered over the last five years. Those reforms have helped to generate record rates of employment and in particular a substantial reduction in workless households …”

“I have for some time and rather reluctantly come to believe that the latest changes to benefits to the disabled and the context in which they’ve been made are a compromise too far…I hope as the government goes forward you can look again, however, at the balance of the cuts you have insisted upon and wonder if enough has been done to ensure we are all in this together”

The last line is a reference to the government’s slogan “we’re all in this together,” intended to persuade the country that cuts are required across the board given austerity in the of the global financial crash of 2007.

Chancellor George Osborne will find Duncan Smith’s exit a blow to his chances of assuming the leadership of the party, having had his new budget openly criticized by a top colleague.

It is unlikely that Duncan Smith – often nicked ‘the quiet man’ – will go quietly to the backbenches. As a prominent figure in the ‘Leave Europe’ movement, he will likely turn up the volume from that rostrum.

The UK’s opposition party, Labor, responded to the sudden resignation by claiming it is indicative of a party “in disarray.” Opposition leader, Jeremy Corbyn, said: “The resignation of Iain Duncan Smith reveals a government in disarray and a chancellor who has lost the credibility to manage the economy in the interests of the majority of our people.”