Ms Polyakova, an actress and restaurateur, is said to have been in a relationship with Lavrov since the early 2000s and documents unearthed by the foundation show she has been abroad with the foreign minister more than 60 times, including on diplomatic missions.

Her family’s lifestyle and growing multi-million-pound property portfolio is alleged to have been bankrolled by her lover. Miss Kovaleva’s now-deleted Instagram account shows her relaxing on a yacht owned by Deripaska.

Miss Kovaleva bought Kensington apartment in cash

A profile of the 26-year-old on the Imperial College website reveals that she had studied for a master’s in Economics & Strategy for Business in 2018 after working for Gazprom, the Russian oil giant.

In 2016, Miss Kovaleva, then aged 21, paid cash for a £4.4 million apartment on Kensington High Street.

Ms Pevchikh asked: “Can anyone explain how this is possible?

“Polina has to pack her Louis Vuitton suitcases, say goodbye to her British life and leave the UK. Should she not be able to explain where she got the £4.4 million from, her property must be arrested under the Unexplained Wealth Order procedure.”

Miss Kovaleva could not be reached for comment on Thursday.

Liz Truss is planning to unveil the next tranche of sanctions as early as next week, with at least half a dozen names expected to be added to the list, once the Economic Crime Bill becomes law.

The Government does not comment in advance on the target of sanctions, partly for legal reasons, and partly to avoid tipping off oligarchs and allowing them time to move their assets out of the country.

However, Britain has made clear its intention to sanction the 351 members of the Duma who voted to recognise Donetsk and Luhansk as independent, thereby undermining Ukrainian sovereignty.