IAIN Duncan Smith is urging Philip Hammond to rethink a key pledge from his Budget.

The MP for Chingford and Woodford Green has become the most senior Tory to criticise the Chancellor’s National Insurance Contributions (NICs) increase.

Speaking on Sky’s All Out Politics, he voiced his concern about the NICs increase and the cut in the dividend tax allowance.

This will lead to people who set up their own companies paying more tax.

Both measures hit “people who choose an enterprise process,” Mr Duncan Smith said.

He then called for Mr Hammond to review them at the next autumn budget.

He added: “I would like for this period to have a chance to reflect on that.

The former leader also said it was a mistake to offer a categorical promise at the General Election not to raise national insurance.

He said: “I think there is always a problem if you make an absolute pledge at the time of an election and then you subsequently don’t keep it.

“We all saw what happened to President Bush senior, 'read my lips', so some of us were slightly concerned at the time about making pledges that lock you in.”

Mr Duncan Smith also called for the Treasury to show some more optimism about Brexit.

He added: “My sense of the problem here is that the Treasury is still way too pessimistic about the future and isn’t looking at the opportunities.”