Britain's Prime Minister Boris Johnson has come under pressure for his close ties to Russian-born media mogul Evgeny Lebedev.

Johnson must answer "serious questions" about the fact that he has appointed Lebedev baron and thus given him a seat in the House of Lords, opposition Labor leader Keir Starmer told Sky News on Sunday.

According to the Sunday Times newspaper, Johnson had ignored warnings from the secret service MI6 in connection with the granting of a peerage to Lebedev.

Johnson is said to have been friends with Lebedev since he was Mayor of London.

According to the Sunday Times report, the prime minister ignored warnings from MI6 when he made Lebedev baron in 2020.

Starmer said: "In the light of today's further revelations, I think the Prime Minister has serious questions to answer: what did he know?

And has he defied the advice of the security authorities?”

Among other things, Johnson's visit to Lebedev's Italian villa in April 2018 is currently arousing criticism. At the time, Johnson was Foreign Secretary.

Lebedev also attended an important meeting of Tory politicians two years earlier, at which Johnson and his party colleague and current Cabinet Secretary Michael Gove discussed the Conservatives' position in the then-upcoming Brexit referendum.

Gove defended the Prime Minister against criticism on Sunday.

Lebedev made it clear in the newspaper he owns, the Evening Standard, that he "wholeheartedly rejects" the war in Ukraine.

Lebedev, who has both Russian and British citizenship, called on Russian President Vladimir Putin on Monday to withdraw troops from Ukraine.

In the past, however, the media mogul has been less critical of the Kremlin.

He described the Syrian mission of the Russian army as correct.

He also publicly questioned the notion that Russian agents poisoned former KGB officer Alexander Litvinenko in London in 2006.

Britain has imposed sanctions on seven Russian oligarchs over the Ukraine war.

Among others, the owner of the London football club Chelsea, Roman Abramovich, is affected.

On Sunday, the government in London also announced a new program to take in Ukrainian refugees.

Under the Home for Ukraine program, “tens of thousands” of Ukrainian refugees will be able to live in British homes for up to three years and also have access to the labor market, health care and education, Cabinet Secretary Gove said.

Great Britain has recently come under international criticism for its comparatively restrictive policy towards Ukrainian refugees.

According to Gove, 3,000 visas have been issued to Ukrainian refugees so far, allowing them to join relatives in the UK.