Workers in North Norfolk could be the hardest hit by the chancellor's controversial National Insurance Contribution revenue raiser.
Figures show the area has the highest proportion of self-employed workers in the region, who could see their tax bills rise after Philip Hammond unveiled plans for a 2pc hike in Class 4 national insurance contributions for the self-employed.
The move has been criticised by opposition MPs and a number of the government's own backbenchers.
Figures show that almost one in six people in the North Norfolk constituency class themselves as self-employed.
But the government has insisted that the move is fair in the light of the abolition of the separate Class 2 payments as well as improvements to the benefits received by self-employed people.
A review of modern employment practices by RSA chief executive Matthew Taylor, due to report over the summer, will be followed by a Government paper which is expected to include proposals to extend benefits such as parental leave to the self-employed.
But North Norfolk MP Norman Lamb said: 'These changes will come as a major shock the thousands of self-employed people in Norfolk already facing a hit to living standards from rising prices.
'The Conservatives have broken a clear manifesto pledge.'
In a Brussels press conference on Thursday, the prime minister promised to listen to concerns raised by Conservative MPs and said there would be no vote until the autumn on the £2 billion hike in NICs for the self-employed.
She acknowledged that the Budget had meant 'difficult decisions' but insisted it was vital to close the gap between the amount of tax paid by the self-employed and those in 'traditional' employment.
The rise in people in self-employment risked eroding the tax base, leaving public services short of funding, she warned.
And 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.' Labour has opposed the move.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here