Theresa May has defended the Budget's controversial National Insurance hike, insisting it would make the system fairer by closing the gap between employees and self-employed workers.

The Prime Minister's intervention came as Tory MPs voiced concerns about the the £2 billion hit on the self-employed announced by Chancellor Philip Hammond.

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Mrs May said the full effects of the reforms would be set out in a paper this summer and Mr Hammond would "listen to the concerns" raised by MPs and business.

But at a press conference in Brussels, she said: "This is a change that leaves lower-paid self-employed workers better off, it's accompanied by more rights and protections for self-employed workers and it reforms the system of National Insurance to make it simpler, to make if fairer and to make it more progressive."