The House of Commons passed government plans for £12bn in welfare cuts last night, including tax credit cuts and welfare caps, while acting Labour leader Harriet Harman suffered a rebellion in the vote.
After five hours of debate, Parliament backed the Conservatives' Welfare Reform and Work Bill by 308 votes against 124 votes.
But 48 Labour MPs went against their orders of abstaining from the vote and voted against the bill.
London mayoral candidates David Lammy and Sadiq Khan voted against the bill, while Labour leadership hopeful Jeremy Corbyn also voted the bill down.
Meanwhile, Corbyn’s competition for leadership of the Labour party – Andy Burnham, Yvette Cooper and Liz Kendall – all abstained.
Chief secretary to the Treasury Greg Hands, tweeted:
47 Labour rebels on welfare tonight. Huge. Biggest Labour rebellion for some time. Leadership crisis without actually having a Leader!— Greg Hands (@GregHands) July 20, 2015
Speaking after the vote, secretary of state for work and pensions Iain Duncan Smith said:
"Nearly 50 Labour MPs have defied their leadership and opposed our welfare reforms which will move our country from a low wage, high tax and high welfare economy to a higher wage, lower tax and lower welfare society.
"It's clear that Labour are still the same old anti-worker party - just offering more welfare, more borrowing and more taxes."