Britain’s richest man, the Brexit supporter Sir Jim Ratcliffe, and two of his key lieutenants at chemicals firm Ineos have reportedly been planning to save up to £4bn in tax after moving to Monaco.

The company, which is valued at about £35bn, is working with tax experts at PricewaterhouseCoopers (PwC) to create a new structure for the business to dramatically reduce the tax paid on its global revenues, according to the Sunday Times.

Ratcliffe, who has lobbied to weaken green taxes and reduce restrictions on fracking, owns 60% of Ineos, which made profits of more than £2.2bn last year and employs 18,500 people. His top two lieutenants at Ineos, Andy Currie and John Reece, each own 20% of the company worth £7bn and were also reported to be moving to Monaco and involved in the tax avoidance plan.

It emerged last year that Ratcliffe, the founder and chief executive of Ineos, was preparing to move to the tax-free principality on the Côte d’Azur, but the latest reports indicate exactly how much the three could save – putting the minimum at £440m.

Ratcliffe’s cash-saving shift abroad comes despite vocal support for Brexit in the run-up to the referendum in 2016 when he said: “Never forget that we have a decent set of cards.”

The details of his plans have emerged as the Brexiter James Dyson moves his business base to Singapore. PwC, which was at the heart of the Luxleaks scandal that revealed complex tax avoidance schemes created for clients including Dyson and the drugs firm Shire, has faced criticism for constructing “labyrinthine” tax avoidance structures that have saved clients millions of pounds in saved revenues.

The Liberal Democrat leader, Sir Vince Cable, described Ratcliffe’s move as “deeply cynical”.

“The idea we should be dishing out knighthoods to people who have no commitment to this country is rather shameful,” he told the Sunday Times.

John McDonnell MP, the shadow chancellor, said he was “really disappointed” by Ratcliffe’s move to Monaco to save tax.

“I’m amazed, as this is a super-rich person. We’re not talking about someone who is on his uppers or something like that.

“For every penny that is avoided in this way in taxation, what does that mean? It means actually the NHS doesn’t treat patients as well as they could, it means our children don’t get the full investment in their education and it means less safety on our streets

“I just appeal to people like this, this is a great country to live in, just make your contribution like the rest of us.”

Prem Sikka, a professor of accounting and finance at the University of Sheffield, said Ineos could employ a range of structures to reduce tax such as diverting dividends to Monaco, where they would not be liable for UK tax, to schemes in which inter-company loans or royalty fees reduced the profits of the UK-based business, diverting cash to offshore tax havens.

Facebook Twitter Pinterest In 2010, Ratcliffe moved Ineos’s official head office to Switzerland for six years after a row with the government over tax. Photograph: Andrew Milligan/PA

“There are numerous possibilities for shifting profits and Ineos is no stranger to these things,” he said. In 2010, Ratcliffe moved Ineos’s official head office to Switzerland for six years after a row with the government over tax.

Robert Palmer, the executive director of campaigning group Tax Justice UK, said it was “sad” that Ratcliffe had “put his own greed ahead of contributing to this country. It just reinforces the feeling that lots of people have that the economy is not geared for them. Lots of people are feeling left behind and this helps reinforce that idea that the rules are not written for them but for wealthy individuals.”

PwC declined to comment on the reports, which suggested the advisory firm had considered quitting. “PwC can confirm it did not consider there was any reason to terminate its relationship with Ineos,” a spokesperson told the Sunday Times.

According to the Ineos annual report for 2017, the most recent available on its website, PwC received £5.1m in fees from Ineos that year, slightly down from £5.8m a year before. The fees included £1.7m related to tax advice compared to £700,000 for auditing its annual accounts.

Ratcliffe was ranked the UK’s richest person in May after he contacted the editor of the Sunday Times rich list to complain that his wealth had been drastically underestimated.

The list increased its estimate of his wealth by £15.3bn to £21bn, catapulting him from 18th to top of the list, after he provided access to the privately held accounts of Ineos, which he founded in 1998. The newspaper also increased its valuation of his mansion near Beaulieu in the New Forest, and his two superyachts, called Hampshire and Hampshire II.

Ineos did not respond to requests for a comment.