UK lawmakers are at risk of being influenced by the Kremlin as lobbying rules do not prohibit approaches from firms linked to the state, an MP has said.

Although Russian businesses and hundreds of oligarchs have been banned from operating in the UK, firms with links to them or the Kremlin can still approach peers and MPs in an attempt to influence the law in Britain.

Alyn Smith, the SNP's foreign affairs spokesman, has written to the government's anti-corruption champion and the Commons speaker asking for a review of the rules and urging them to close this route of potential influence.

He said there is nothing currently in place to stop lobbyists working for firms backed by the Russian government from making approaches to parliamentarians.

In letters to Commons Speaker Lindsay Hoyle and Tory MP John Penrose, the government's anti-corruption tsar, Mr Smith said he had "grave concerns" that the current rules were not acting as a deterrent for lobbyists.

He said: "In light of Russia’s barbaric and illegal invasion of Ukraine, the urgency to implement long overdue legislation becomes all the more necessary."

He said the current register of parliamentarian's interests, where MPs have to record meetings with lobbyists "does not operate as an adequate barrier or deterrent to prevent Parliamentarians in Westminster from representing the interests of the Kremlin in the Chamber of the House of Commons and indeed the House of Lords."

The MP for Stirling gave the example of one peer, Greg Barker, who resigned earlier this month as chairman of EN+, a mining company part-owned by Russian ologarch Oleg Deripaska.

Mr Deripaska has been sanctioned by the UK Government as part of its package of penalties against more than 1000 oligarchs and firms linked to the Kremlin.

Lord Barker was an energy minister in David Cameron’s government and helped the company respond to US government sanctions imposed on them and on Deripaska in 2018, claiming he had links to the Russian government.

Mr Deripaska has previously said the US allegations were based on “false rumour and innuendo”.

Mr Smith explained: " Sadly, examples of this problem are not difficult to find.

"Lord Barker – a Conservative peer – stepped down as chairman of EN+ Group. This company is the London-listed owner of Rusal, a Russian aluminium company, and the world’s second largest aluminium company. It is owned by Oleg Deripaska, who enjoys close ties to Vladimir Putin. "

He continued: " The US sanctioned EN+ in 2018 due to its suspected affiliation with the Kremlin; Lord Barker actively sought solutions to help the company respond to these challenges.

"Lord Barker earned $4 million and $7.8 million from EN+ in 2020 and 2019 respectively, and even attended COP26 in Glasgow as part of the Russian Delegation.

"I fear Lord Barker is but one example of a far wider and more endemic problem within the Houses of Parliament.

"These changes cannot and must not be guidance. They must come as official changes to Parliamentary Standards procedures."

Lord Barker announced he would be standing down as EN+ chairman on March 7, with the firm

Prior to his departure, the UK defence secretary Ben Wallace said he should give up any roles linked to Russia, adding: “I think Lord Barker should explain why he works with people like Deripaska,”

Mr Smith has asked whether any "urgent reviews"w ere now taking place of the parliamentary lobbying rules, and asked for confirmation that "all officials from Russian companies, banks and organisations sanctioned by the UK Government, will be banned from lobbying Parliamentarians in both chambers of the House of Parliament."

He also said this should be extended to cover firms linked to the Belarusian government, an ally of Putin.

The Commons Speaker and Mr Penrose were approached for comment.