Treasury Minister Jane Ellison was forced to defend her party after being accused of breaking an election promise.
On Wednesday, Chancellor Philip Hammond revealed he would increase Class Four National Insurance Contributions (NICs) by two per cent over the next two years.
He argued the increase would help make the tax system fairer, but critics branded the move as a tax on the "White Van Man".
Jon Snow snapped at Tory minister Jane Ellison during a heated row on Wednesday
This brings politics into disrepute – you’ve lied
As the controversial announcement was put under the spotlight on Channel 4 News, Ms Ellison was accused of bringing “politics into disrepute” by backtracking on a manifesto pledge not to increase taxes by host Jon Snow.
The Tory minister claimed the party’s promise only covered Class One NICs, a tax automatically deducted by a worker’s employer.
She said: “Class One is the one paid by the vast majority of people, 85 per cent, we then went on to legislate in the House of Commons.
“So we made it very clear what we were doing – we were looking at Class One.”
The treasury minister was accused of breaking an election pledge
In 2015, George Osborne, the then chancellor, said it was a “Conservative pledge” for there to be “no increases in national insurance”.
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A “tax lock” legislation, which banned tax rises until May 2020, was later introduced by the Tories in September 2015.
Clearly not happy with the response, a tetchy Jon Snow fumed: “This is after you’ve told voters ‘we will not raise it’, but you have!
“I’m sorry but either this is a promise or it isn’t and this, of course, brings politics into disrepute – you’ve lied!”
Jon Snow accused the Conservatives of bringing "politics into disrepute"
Mr Hammond believes the tax raid on the self-employed will raise £145m a year by 2021-22.
He said the move was necessary because self-employed people pay less NICs but still benefit from the same level of public services, such as access to the NHS.
Ukip's economy spokesman Mark Reckless blasted the move – warning the Conservatives have "lost any claim they represent White Van Man".
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Mr Hammond says he is 'building the foundations of a stronger, fairer, more global Britain'
In a statement, Mr Reckless said: “In this Budget, Philip Hammond has launched an unnecessary and foolish attack on enterprise. To claim to be making life better for the employed by making life worse for the self-employed is the worst kind of levelling down.
“It is an approach more befitting of big state socialism than of a party that claims to understand wealth creation.
“Self-employed people create their own jobs. They have no paid holidays, sickness benefits or company pension schemes and in fact no guaranteed income at all. They show guts and determination.”