Labour leader Jeremy Corbyn missed the political equivalent of an open goal at Prime Minister's Questions on Wednesday (15 March).

The UK government's and Philip Hammond's credibility took a major blow when the Chancellor U-turned over his plans to raise National Insurance Contributions (NICs) for self-employed workers, just a week after his Spring Budget.

But Corbyn was not able to capitalise on the embarrassing climb-down as he attempted to grill Theresa May in the House of Commons. "We've just heard the prime minister is about to drop the [NICs] hike announced only a week ago," he told MPs.

"it seems to me like a government in a bit of chaos here. A Budget that unravels in seven days, a Conservative manifesto with a very pensive prime minister on the front page saying there would be no increase.

"A week ago an increase was announced. If they are to drop this increase, as they are indicating, then this is a time she should thank the Federation of Small businesses (FSB) and all of those who pointed out just how unfair this increase would be, but also how big business evades an awful lot of National Insurance through bogus self-employment."

May hit back: "I normally stand at this dispatch box and say I won't take any lectures from the right honourable gentleman. But when it comes to lectures on chaos, he would be the first person I would turn to."

Corbyn later used his final three questions to address the social care "crisis", public services spending and called for a "staircase for all" in opposition to May's grammar schools plan.

But Yvette Cooper, Corbyn's former Labour leadership rival and Home Affairs Committee chair, was able to take May to task.

"The prime minister's just done a £2bn ($2.4bn) Budget U-turn in the space of a week," she said. "Last year the government did a £4bn U-turn in the space of five days, is that why they want to abolish Spring budgets because they just keep ripping them up?"

Hammond's future in Number 11 now looks uncertain. The Chancellor broke a key pledge his party's 2015 general election manifesto and other Conservative MPs may be angered at his sudden U-turn.