The average number of new tax cases sent to the Court of Justice of the EU (CJEU) has risen by a fifth since the credit crunch, up from an average of 50 per year between 2005 and 2010 to an average of 61 per year between 2011 and 2015, according to figures obtained by firm.

Pinsent Mason’s analysis suggests the increasing number of such claims could be down to the pressure national tax authorities have been under to increase revenues, leading many to levy extra charges and ensure that they maximise tax take wherever possible.

Andrew Scott, a tax expert at Pinsent Masons, said: ‘The reach of EU law has widened considerably and continues to do so, with the result that an increasing amount of UK tax law is affected. More businesses and other taxpayers have therefore managed to find grounds for challenging UK tax law.

‘Although it's business as usual at present, Brexit means that the power of the CJEU over UK law will end but at an unknown time in the future. UK claimants will therefore be considering whether to launch proceedings now so as to increase the likelihood that their claims are protected as and when the UK does leave the EU.’

In particular, UK businesses might have concerns that the UK government would attempt to remove the ability to bring a claim based on EU grounds without notice, ‘even where EU law applied at the relevant time’, as it had done in the past, Scott said. For this reason, companies would be keen to begin proceedings while it is clear that EU law still applies in the UK, he said.

HMRC and the UK government will continue to be bound by EU tax legislation until the Brexit process is complete. However, challenges based on the laws that were in force at the relevant time, including EU laws that were later reversed, would continue to be valid unless the UK passed separate legislation abolishing historic EU-law based tax refund claims, Pinsent Masons said.