The boss of Revolut has said it is “not rational” to list its shares in the UK over the US, dealing a blow to London’s stock markets following the fintech giant becoming Europe’s most valuable start-up.

Nik Storonsky’s remarks came as the chief executive of Barclays said London’s stock market had “shrunk” over the past decades, while “the US has grown”.

The co-founder and chief executive of Revolut said “sooner or later” the company will want to consider floating on the public market in order to raise cash to return money to shareholders.

Speaking on the 20VC podcast, he said it was less attractive to list in London because of the 0.5% tax rate on most transactions when people buy shares in the UK.

“The problem with the UK is, if you think about it versus the US, it is much more illiquid, and trading in the US is free… so I just don’t understand how the product which is being provided by the UK can compete with the product that is being provided by the US.

“It is less liquid so it is much worse compared to the US, plus it is more expensive because you pay stamp duty, it is just not rational.”

Revolut clinched a valuation of 45 billion dollars (£35.6 billion) via a share sale by its employees in August, confirming its position as the most valuable start-up in Europe.

It came after securing a UK banking licence, ending a three-year wait for approval to operate as a bank in its home market.

Meanwhile, Barclays’ chief executive CS Venkatakrishnan, known within the bank as Venkat, said the UK equity market had “seen structural decline for more than 30 years”, and had “shrunk… while the US has grown”.

“We’re going to have to invest now, and hope our children’s generation get the advantage of it, because it’ll take time,” he said.

Venkat nevertheless stressed that London is a “great financial centre” which will attract significant activity, adding that the global bank wants to “identify deeply with the city and the country”.