The volume of ISA millionaires was discovered by financial advisory network The Openwork Partnership, after a freedom of information request from the HMRC. The figure of just over four thousand ISA millionaires is more than twice as many as the previous record, which was 2,000 four years ago. In 2016, the number of  ISA millionaires stood at just 450.

Almost all of the millionaires are thought to be investors in stocks and shares ISAs.

The information from the HMRC disclosed that the average ISA millionaire is sitting on a pot that is worth £1,397,000. The 50 top investors overall have accumulated average pots of £8,509,000.

The record figure comes soon after the passing of former Chancellor Nigel Lawson three months ago, who introduced the ISA,then known as personal equity plan or PEPS in 1987. At the time, there was an investment limit of £2,400.

ISAs have “empowered millions”

Setul Mehta, the head of partnership services at The Openwork Partnership said: “The ISA has not only created thousands of millionaires, but it has also empowered millions of ordinary investors to build a nest-egg alongside their pension. It is perhaps the best tax-free investment wrapper in the Western world.

“Of course, becoming an ISA millionaire takes time, money and a little bit of knowledge. But the rise in personal finance content online means the roadmap to millionaires’ row has never been more clearly signposted.

“A stocks and shares ISA holder consistently maxing out their £20,000 allowance could reasonably expect to smash through the seven figure mark after around 22 years assuming average returns of seven per cent per annum. If Nigel Lawson is looking down, then there can be no doubt he will be feeling more than a little chuffed with these figures.”