The outraged Labour MP blasted the Chancellor after he announced self-employed workers paying the main rate of class 4 National Insurance contributions would see an increase by 1 per cent to 10 per cent in April 2018.
An 11 per cent increase in April 2019 is set to follow, altogether raising £145million a year by 2021/22 at an average cost of 60p a week to those affected.
The Jeremy Corbyn faithful branded the budget announcement “grotesquely unfair” and argued it would hit middle to low earners the worst before he was taken down over the strength of his party.
Speaking on BBC Radio 4’s Today programme, host Justin Webb suggested Labour MPs felt the Government was only able to introduce such measures because the party was “weak”.
John McDonnell vowed to work with MPs across the Commons to overturn the decision
I’m hoping there will be a number of Conservative MPs and other parties in the House that say to the Government ‘you’ve got this wrong, you need to think again’
“It’s weak in the polls, it lost Copeland,” he added. “Do you have a sense of that being important? Actually, the way to fight against these things is to get labour back into a position where it could actually win a general election.”
But Mr McDonnell refused to accept his party was “weak” and insisted the Labour Party would fight the changes “at every opportunity”.
He replied: “Well it’s interesting because last year we defeated the Government on a whole series of proposals when they were trying to cut benefits to working people.
“That’s what I’m hoping we’re going to do on this. I’m hoping there will be a number of Conservative MPs and other parties in the House that say to the Government ‘you’ve got this wrong, you need to think again’.
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Budget 2017: Philip Hammond hailed Britain’s booming Brexit economy today as he delivered his first Budget of the year
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Mr Hammond says he is 'building the foundations of a stronger, fairer, more global Britain'
Philip Hammond during Wednesday's budget announcement
“That’s why we’ll be voting against this when this comes forward and we’ll be opposing it at every opportunity within the Commons and the Lords.”
The shadow chancellor maintained it was the “wrong policy” with it also reducing the “same access to the same level of benefits”.
He added: “Someone on £20,000 is going to be paying £260 more – you go up to £40,000, it’s considerably more.
“These are not people on high wages, they’re middle to low earners, they’re the people in the largest numbers that will be affected by this – it should’ve been properly consulted on.”