Jeremy Corbyn has said the British government needs to fund Northern Ireland's welfare system properly and warned of increased poverty because of Tory plans.
The devolved powersharing administration in Belfast is at an impasse over measures to cut the cost of benefits, which the government says are necessary to reduce the deficit and encourage work but Sinn Fein believes will hurt the most vulnerable.
Labour leadership frontrunner and anti-austerity campaigner Mr Corbyn will be in west Belfast tonight to speak at Féile an Phobail.
He told BBC Radio Ulster's Nolan Show: "The British government is the one that should step up to the plate on this because what they are essentially doing is not providing either the resources to the Assembly to fund the welfare system properly or allowing the Assembly to do it itself with the money, so we need a change by the British government more than anything else."
Mr Corbyn attracted British criticism in the 1980s for his support of Sinn Fein and a united Ireland.
He was a champion of the Birmingham Six and Guildford Four before their releases.
The leadership candidate is appearing at the Feile tonight as part of a panel discussion, which is likely to include the political stalemate at Stormont.
Sinn Fein and the DUP are at odds over aspects of the Stormont House Agreement, which was supposed to pave the way for welfare reforms and various other changes.
Mr Corbyn has burnished his credentials with the Left by defying acting leader Harriet Harman to vote against the government's Welfare Bill.
The other leadership candidates fell into line by backing the Opposition's "reasoned amendment" to the legislation - which was defeated - and then abstaining on whether it should progress to the next Commons stage.
He said: "It seems to me that we should not be allowing the welfare reform Bill to go through in the British Parliament.
"Essentially this is a budget issue at the present time and the British government should be funding Northern Ireland properly."
He said there would be increased poverty because of the welfare plans.
The British government has not said the north's ministerial Executive cannot fund an enhanced welfare system but has maintained it is not prepared to pay for more expensive arrangements than in the rest of the UK.
