BRITAIN'S richest man who owns the huge petrochemical site at Grangemouth is understood to be leaving the country to live in low-tax Monaco.

Sir Jim Ratcliffe, the 65-year-old boss of Ineos who was knighted this summer, has not revealed the reason for his move, but already owns a mansion on the French Riviera.

The high-profile Brexit supporter who was named as the UK’s wealthiest individual in the 2018 Sunday Times Rich List, with a fortune of £21.1 billion.

Mr Ratcliffe has not responded to requests for comment, and a spokeswoman for Ineos declined to comment on his decision describing it as a “personal matter”.

Ineos did say it was “committed” to its business base in the UK and planned to keep its headquarters in London “for the foreseeable future”.

HeraldScotland: Ineos boss Jim Ratcliffe said ‘the Scottish Government needs to get comfortable with whether they’re happy with the risks of fracking in Scotland’

The petrochemicals engineer, who founded Ineos, the huge privately owned chemicals group, in 1998, tried and failed to get Scotland’s fracking ban overturned using the courts, and he had previously been heard complaining about the tax and business environment in the UK.

Two other Ineos executives Andy Currie, a director, and John Reece, finance director, are expected to move to Monaco too, according to the Daily Telegraph.

Mr Ratcliffe’s exit comes after Nigel Lawson, the former Chancellor and long-term Brexiteer, applied for permanent residency in France.

HeraldScotland: INEOS 1 SA :  INEOS Founder and Chairman Jim Ratcliffe holds a press conference at their Grangemouth office, as the First US shale gas arrives in the UK. The Ineos Insight gas carrier arrives at Grangemouth with the first shipment in a 'virtual pipeli

In the run-up to the Brexit referendum, Ratcliffe provided a boost for the Leave campaign when he said Britain would thrive outside the EU.

He recently said that he looks forward to Britain throwing off the shackles of Brussels when we finally quit the EU.

He said: "The Brits are perfectly capable of managing the Brits and don't need Brussels telling them how to manage things.

"I just don't believe in the concept of a United States of Europe. It's not viable."