Traders have criticised the Chancellor for increasing national insurance contributions for the self-employed in the Spring Budget.

Philip Hammond was accused of breaching the Government’s manifesto promise two years ago when the Tories pledged not to increase the tax for five years.

Instead, the Chancellor told the Commons on Wednesday he would increase the 9% levy on the profits of self-employed people to 10% next year and then 11% in 2019, raising an extra £2 billion in tax revenue.

Mr Hammond said the lower national insurance paid by the self-employed is forecast to cost the public purse more than £5 billion this year, which is not fair on the 85% of workers who are employed and pay higher taxes.

He said: “Such dramatically different treatment of two people earning essentially the same undermines the fairness of the tax system.

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“Employed and self-employed alike use our public services in the same way, but they are not paying for them in the same way.”

Craig Harman, a tax specialist at Tunbridge Wells-based Perrys Chartered Accountants, said the Chancellor’s move would leave those worst affected out of pocket by £700 a year when the 11% levy comes into force in 2019.

“Many entrepreneurs and sole traders will be disappointed to see significant rises to their national insurance bills over the coming years..." - Jo James, Kent Invicta Chamber of Commerce

He said: “The increase in Class 4 National Insurance contributions for the self-employed would appear to be a blatant breach of the Government’s manifesto pledge from two years ago, which promised not to increase NI for the next five years.”

Jane Ollis, chairman of the Institute of Directors Kent branch, felt it was a “lacklustre” Budget and criticised the national insurance tax as potentially stifling new business.

She said: “It is focusing people down the employed route rather than self employment.

“There was nothing in there to boost the types of business we need post Brexit which will be trading globally and scalable.”

Jo James, chief executive of Kent Invicta Chamber of Commerce, said: “Many entrepreneurs and sole traders will be disappointed to see significant rises to their national insurance bills over the coming years.

“Ministers need to ensure that these business people, who make a significant contribution to the economy, also get the recognition and benefits that correspond to their contribution.”

Ben Stepney, senior associate at law firm Thomson Snell & Passmore, which has offices in Dartford and Tunbridge Wells, said: "As was widely expected, the Chancellor moved to narrow the difference in tax treatment of employees and the self-employed.

"This discrepancy may seem unjustified on the face of it, but it is worth remembering that those who are self-employed do not enjoy the job security, employment rights and access to benefits in kind available to employees.

"Part of the trade-off for self-employed workers has traditionally been that they get preferential tax treatment to compensate for the risks they take on.

"This change will come as a blow for many (often low-paid) workers in the gig economy who are treated as self-employed and who already suffer from lack of job security and day-to-day uncertainty about whether there will be enough work available for them."