In a television interview, Maugham said he was bringing the legal case in order to ascertain whether the UK's tax authorities give big US companies special license when it comes to tax.

‘I'm suing Uber to understand whether HMRC treats these big US multinationals, including Uber, with kid gloves,’ he said.

Uber, which describes itself as a platform that connects riders and drivers, has said it is not providing a transportation service and so it does not pay VAT.  Any drivers who earn above the VAT threshold are responsible for their own tax.

However, Maugham argues that ‘the taxable supply is being made by Uber’, claiming that this view was supported by an employment tribunal that last year found Uber drivers were employed by Uber rather than self-employed as Uber said. Uber has appealed against this decision.

In a blogpost, Maugham said: ‘On the assumption that the VAT reality of Uber’s business is that it is engaging drivers and supplying transport services to passengers, the vast majority of its expenditure will be the money it pays to drivers. But (with perhaps a tiny number of exceptions) drivers don’t charge Uber VAT on their fares.

‘If you assume that Uber has no material input tax to set against its output tax, which would mean that, of every £100 of fares Uber has collected, it has a liability to pay VAT to HMRC of £16.67.’

He calculated that Uber collected about £115m in fares in 2015, which would produce a VAT liability of just under £20m for London for that year. Maugham pointed out that HMRC would be able to inquire into the past four years of accounts to discover the VAT status, while he also suggested that similar issues could be raised in other EU countries in which Uber operates.

Uber has declined to comment on its VAT position pending its appeal over the employment tribunal decision. It has released a statement saying: ‘Drivers who use the Uber app are subject to the same VAT laws as any other transportation provider in the UK.’

In Australia, Uber has recently lost a federal court case over whether its drivers should be charged goods and services tax (GST), in a case with some similarities.

Usually, businesses that earn less than $75,000 (£46,000) per year are exempt from GST, but taxi firms are specifically left out of this relief.  The Australian Taxation Office had counted Uber drivers as taxi drivers, but the company challenged that interpretation in the courts.

Uber claimed most drivers earnt less than $20,000 a year and were not driving taxis as the vehicle could not be hailed off the street or via a taxi ranks. However, the court agreed with the tax authority that the term ‘taxi’ has a broader definition and did cover ridesharing services, meaning Uber drivers do have to pay the tax.

Maugham’s blogpost is here.