BILLIONAIRE Chelsea boss Roman Abramovich may be asked to account for his vast wealth before being allowed back into the UK, it has been claimed.

The oligarch is currently unable to get back into Britain owing to the fact his visa has not yet been renewed - with the Kremlin accusing Britain of "anti-Russian mania".

Those close to Moscow-based Abramovich insist his request for a new visa has simply been delayed by the Home Office rather than denied.

It appears he may have been caught up in a clampdown - sparked by the Skripals' poisoning - on dirty money flowing into Britain and is now being treated as a new applicant, but there is no suggestion of any wrongdoing on his part.

However Abramovich - Britain's 13th-richest man - will be asked to prove how he made his billions, The Times reported.

According to the paper, he will also be asked to prove that his “character, conduct or associations” contribute to the public good.

Since 2015 the Home Office can refuse these visas if they have reasonable grounds to believe an applicant's funds were obtained unlawfully.

The delays have thrown his future in Britain and his ownership of Chelsea FC into doubt, and lawyers say red tape is unlikely to have been the cause of the delay.

This might be due to the fact the Home Office has a "super-premium service" which allows those willing to pay thousands of pounds to have their visa applications assessed within a day.

It comes amid heightened tensions between Downing Street and the Kremlin after the assassination attempt on ex-spy Sergei Skripal and his daughter in Salisbury.

The attack plunged relations between the two countries to the lowest they've been since the Cold War and led to the expulsion of more than 100 Russian spies from the West.

It also was the most brazen of many recent Kremlin plots, including cyberhacking and election interference, designed to undermine the West which UK politicians have now vowed to halt.

Moscow has also hit back at Britain after MPs released a report accusing the government of "turning a blind eye" to Russian money being hidden in British assets.

Putin's spokesman Dmitry Peskov said: "We are witnessing Britain's rather unprecedented anti-Russian mania which is manifested in various ways.

"I have no doubt that such actions won't go unnoticed by investors from other countries.

"Many countries are working to improve their investment attractiveness and this I believe is a step in the opposite direction."

Last night it was not clear where Abramovich was, though the Times reported that a jet he uses flew from Moscow to the French Riveria.

Theresa May's spokesman said earlier that the government is conducting a review into "tier one investor visas" believed to be the type held by Abramovich.

The claims "dirty" Russian money is being laundered through the City undermines the government's efforts to take a tougher stance against Moscow's "aggressive foreign policy", say MPs.

May has vowed to clampdown on Russian money but a report by parliament's Foreign Affairs Committee accused her government of failing to back up its threats with action.

"There is no excuse for the UK to turn a blind eye as President Putin's kleptocrats and human rights abusers use money laundered through London to corrupt our friends, weaken our alliances, and erode faith in our institutions," said committee chairman Tom Tugendhat.

"The scale of damage that this 'dirty money' can do to UK foreign policy interests dwarfs the benefit of Russian transactions in the City."

Meanwhile, questions are now being asked as to what the future may hold for Chelsea FC.

Abramovich bought the football club in 2003 for £140m, turning it into one of the world's leading clubs by personally bankrolling its squads.

In recent years, however, he has spent much less time at Stamford Bridge.

He was regularly seen in his owner's box at the start of the season, but has been increasingly vacant throughout 2018.

Although flight records show his private jet was last in London on April 1, his lack of interest may be due to Chelsea's poor second half of the season, rather than a loss of interest in the project as a whole.