Self-employed people currently pay Class 2 national insurance – £2.80 per week on annual earnings of £5,965 or above – and Class 4 national insurance which is 9% on earnings between £8,060 and £43,000, and 2% on anything above £43,000.

Class 2 NICs will be scrapped from April 2018 and today, chancellor Philip Hammond announced that Class 4 NICs will increase from 9% to 10% from April 2018 and by a further 1% to 11% in 2019. The Treasury confirmed there will be no change to the 2% rate for earnings over £43,000 – it remains in place.

He said the average cost for those affected will be 60p a week.

Hammond drew comparisons between the NIC rates paid by an employee and a self-employed worker. He said an employee earning £32,000 will incur between him and his employer £6,170 of NICs while a self-employed person earning the equivalent will pay just £2,300.

Hammond said: “People should have choices about how they work, but those choices should not be driven primarily by differences in tax treatment.

“Historically, the differences in NICs between those in employment and the self-employed reflected differences in state pensions and contributory welfare benefits. But with the introduction of the new state pension, these differences have been very substantially reduced.

“Such dramatically different treatment of two people earning essentially the same undermines the fairness of the tax system. Employed and self-employed alike use our public services in the same way, but they are not paying for them in the same way. That is not fair to the 85% of workers who are employees.”

Tax hike won’t be popular but was expected

Hargreaves Lansdown calculates that a self-employed worker earning £30,000 will pay £282 more NICs in 2019 than in 2016.

Tom McPhail, head of retirement policy, said: “Ever since the state pension changes of 2016, when self-employed workers’ state pensions were brought into line with employees’, this reform has been on the cards.

“This tax hike won’t be popular with the self-employed, though it’s designed to balance out the long-term windfall they received as a result of the new state pension scheme.”

McPhail said that he would like to see the government continue to improve pension provision for the self-employed by bringing them into auto-enrolment, via the self-assessment tax system.

Steven Cameron, pensions director at Aegon UK, said despite state pension changes for the self-employed, employees receive other benefits such as statutory maternity and sick pay from the NI system which the self-employed and those in the gig economy don’t qualify for.

“Looking wider, more needs to be done to close disparities inherent in the current gig economy, and between the employed and the self-employed. Within pensions, we need to find a solution equivalent to auto-enrolment for the self-employed to halt the growing retirement income divide we’ll otherwise face between them and their employed peers when they come to retire. One way forward to soften the blow would be to ‘rebate’ part of the increase in NI into a private funded pension of the self-employed individual’s choice, along the lines of auto-enrolment for employees.”