The move follows increasing concerns by U.S. congressmen over the extent of Russian meddling in both the U.S. and Europe, with a number of oligarchs with close ties to Russian President Vladimir Putin forming the main focus of the inquiry.

Among the UK-based companies that have aroused the interest of congressional investigators is EN+, the energy company owned by Oleg Deripaska and chaired by Tory peer Lord Barker of Battle.

Mr Deripaska, a close ally of Mr Putin, is already under investigation from congressional committees over allegations, which the oligarch denies, that he was involved in efforts to interfere with the 2016 presidential elections.

Recent documents released by the FBI revealed Mr Deripaska loaned $10 million to Paul Manafort, Donald Trump’s campaign manager, who has been charged with fraud and money-laundering. Mr Deripaska is one of several Russian oligarchs who were hit with U.S. sanctions in April.

Now US investigators say they are interested in apparent links between British-based companies owned by Russian oligarchs and Russian intelligence agencies.

Their interest in EN+ comes after FBI officers identified Evgeny Fokin, who is the company’s Director of International Cooperation, as formerly being the SVR’s declared liaison officer with U.S. intelligence agencies in Washington DC in the mid-1990s.

Apart from being employed by EN+, Mr Fokin, who is said to be a close ally of Mr Deripaska, has previously been employed by Basic Element, another company owned by Mr Deripaska.

“There is particular concern in Congress about the links between Russian businesses owned by oligarchs and the Russian intelligence agencies,” a U.S. official told the Daily Telegraph.

“There is concern about the large numbers of former Russian intelligence officers who now hold senior positions in major Russian businesses.

“There are growing suspicions in Congress that the distinction between the Russian state and businesses owned by Putin’s supporters may be on paper only.”

Lord Barker, a former energy minister under David Cameron, provoked criticism from MPs earlier this year after he helped EN+ raise £1 billion on the London Stock Exchange, money that was then used to pay off Russian banks subject to U.S. sanctions.

The claim by FBI officials that Mr Fokin is a former SVR officer would make him the third former Russian intelligence officer to have been identified as working for Mr Deripaska’s business interests.

Valery Pechenkin, another former SVR officer, has been appointed to run Basic Element, while Viktor Boyarkin, a former officer with the same Russian GRU military unit accused of carrying out the Salisbury nerve agent attack in March, has previously worked for Mr Deripaska’s Rusal aluminium conglomerate.

A spokesman for Mr Fokin denied that he had been a member of the SVR, and said Mr Fokin had not been contacted by anyone connected with the U.S. congressional investigation.

A person familiar with the situation told The Telegraph: “Mr Fokin resigned from the Russian Diplomatic Service over twenty years ago to pursue a career in the private sector. He has been with En+ since 2012.”

Both US congressional intelligence committees in the Senate and the House of Representatives have had long-running investigations into every aspect of alleged Russian interference in U.S. elections as well as other organisations.

In October Senator Richard Burr, the chairman of the Senate Intelligence Committee, announced his investigation was looking a new lines of inquiry. Following the outcome of the mid-term elections in November, the Democrat-led House intelligence committee has intensified its inquiry into Russian meddling, with U.S. officials confirming that Mr Deripaska, as well as other oligarchs, remain a particular focus of both investigations.