Theresa May’s government has been accused of attacking aspiration and breaking a manifesto pledge with a raid on the self-employed.

Even Conservative MPs expressed their concerns at the Chancellor's plans to raise the National Insurance contributions of around 2.5 million workers by an average of £240 a year.

Critics also questioned whether voters could believe any future Tory pledges after the party appeared to rely on small-print to justify the U-turn.

The 2015 Conservative general election manifesto pledged to "not raise VAT, National Insurance contributions or income tax".

But the Chancellor announced that that the rate for Class 4 National Insurance contributions, paid on profits of more than £8,060 or more a year, would rise from 9 per cent to 10 per cent next April and to 11 per cent the year after that.

Mr Hammond defended the change saying that reforms to the state pension meant that the self-employed were now receiving higher benefits while still putting in the same amount.

The SNP's economy spokesman Stewart Hosie hit out at what he said was a “scandalous attack on aspiration”.

He said that the measures provided “real hard disincentives to starting business and employing people."

And he predicted that the change was a "decision that will come back to haunt this Chancellor”.

Orkney and Shetland MP Alistair Carmichael said the raid sent the wrong message "while many of these self-employed people are facing huge uncertainty about their future".

Labour’s former shadow chancellor Chris Leslie accused Mr Hammond of breaking a manifesto pledge.

He told other MPs that the “Chancellor needs to explain why he's breaking a manifesto promise made in the 2015 general election manifesto”.

Treasury aides insisted that the government was not breaking a manifesto commitment.

They pointed to the legislation, passed by MPs months after 2015 election, which made mention of a number of classes of NI contribution but significantly not class 4.

Conservative MPs voiced concerns about the reforms and pressed ministers to show that they were on the side of "white van man".

Former Tory minister Andrew Murrison called for reassurances that electricians, plumbers and plasterers would not be hard hit by the changes.

Backbencher Nigel Mills added that it would be unwelcome news among workers "who are probably struggling and not getting all the rights they ought to".

But fellow Tory MP Charlie Elphicke defended the reforms.

He said: "I heard the remarks from the Leader of the Opposition and the SNP saying isn't it appalling, but actually there should be a level playing field, surely, for the self-employed and for the employed.

"That's something about which I feel quite strongly and I think the Chancellor was right to bring in measures."

Mr Hosie also criticised the Chancellor's for what he said was a failure to create an economic buffer for the UK's exit from the European Union.

He said that the Mr Hosie the UK was "completely unprepared" for the "economic tsunami" set to be unleashed by Brexit.

He called the predicted budget surplus “tiny” and predicted that any external shock or capital flight could see “these figures fall apart”.

He also hit out at the Chancellor's confirmation of an extra £350m for the Scottish Government as “smoke and mirrors”, saying that overall spending would still be down by £1bn by the end of the parliament.

Labour leader Jeremy Corbyn accused the Chancellor of "utter complacency" over the state of the economy and what he said was a "crisis" facing public services.

"This is a Chancellor and a Government not on the side of the workers, not on the side of the taxpayers, who pick up the bill for low pay and insecure work," he said.

SNP MP Alison Thewliss also accused the Chancellor of a "missed opportunity" to scarp the government’s controversial 'rape clause' and two child policy.

Tory ministers will restrict tax credit payments to two children per family from April.

As part of the reforms women will have to provide evidence of exceptional circumstances, such as rape, to claim for a third child.

Ms Thewliss said: "I still cannot believe that any government would think it’s acceptable to put women and their families through such incredible pain and misery."

There was also some disquiet on the Tory benches about Mrs May's plans for a new generation of grammar schools.

Mr Murrison warned that the policy could disadvantage other schools.

He told: "I oppose further grammar schools. It would not be good for areas like mine.

"I fear it as a development because of course the flip side of that would be an increase in the number of secondary modern schools, which I don't think has been positive in the past and I would not like to see visited on areas like mine in the future.

"And I would be concerned if the measures announced today, which do appear to advantage, disproportionately, free schools seeking to select their intake, were grammar schools by the back door."

But other Tory MPs welcomed the Chancellor's announcements.

Kit Malthouse, the Conservative MP for North West Hampshire, said: "I have to confess I feel this afternoon as if the Chancellor has dusted off that black polo neck which apparently he used to wear as a young man and delivered to us a box of Milk Tray, such is the delights that we heard about."