The former world chess champion and Russian opposition figure Garry Kasparov has called on Boris Johnson to impose economic sanctions on oligarchs close to Vladimir Putin in response to the poisoning and arrest of the Kremlin critic Alexei Navalny. In an interview with the Guardian, Kasparov said the UK was uniquely placed to take action against Putin’s inner circle. He argued that the flow of money from Moscow into London had to cease. “It’s very simple. Stop talking and start acting,” he said. Kasparov said Russia was at a crossroads following pro-Navalny protests last Saturday in more than 100 Russian cities, with 40,000 people taking to the streets in Moscow. He described the demonstrations as “phenomenal” and the most significant since 1991. “They happened despite state propaganda and pressure on people,” he said. “In Europe nobody can now send a more vocal message to the Kremlin than the Brits. As long as the money keeps flowing into London and to the free world, Putin’s power is untouched.” In the House of Commons on Wednesday, opposition MPs called for sanctions against eight prominent and wealthy Russians cited by Navalny, including the Chelsea FC owner, Roman Abramovich, and Alisher Usmanov, a former Arsenal shareholder with close links to Everton. Margaret Hodge, a Labour former chair of the public accounts committee, told the Commons that Navalny wanted “the international community to use sanctions against complicit Russian kleptocrats”. She said Navalny had named Abramovich and Usmanov as individuals who should be targeted. Sanctions have already been levied against other Russians, including some of those accused of poisoning Navalny with novichok last summer. Hodge said the measures had not worked because “the west has refrained from sanctioning the people with the money”. She was speaking in an emergency debate in the Commons called by Sir Roger Gale, a Conservative backbencher, following Navalny’s detention in Russia 10 days ago and the ensuing protests, which are expected to continue this weekend. Wendy Morton, a junior Foreign Office minister, said: “Sanctions send a clear message to those responsible that the use of chemical weapons is an egregious violation.” She would not be drawn on the individuals named. “Obviously we are considering all options for further action,” Morton said, adding that it would “inappropriate for me to speculate on any future listings”. The UK government has imposed sanctions on the head of the FSB spy agency, Alexander Bortnikov, and five other senior Russian officials, as it firmly believes the agency was behind the poisoning. But it has not yet taken action against oligarchs whom Kasparov and other Russian opposition figures say are closely linked to the Putin regime. Last week Vladimir Ashurkov, a colleague of Navalny in London, released a list of eight influential Russians who Navalny has said should face sanctions. Navalny called on Downing Street to go after “the people with the money”, arguing that “nothing less will make an impact on the behaviour of the Russian authorities”. The Navalny list includes four individuals with significant British connections. Two – Abramovich and Usmanov – are well-known oligarchs. Layla Moran, the Liberal Democrats’ foreign affairs spokesperson, said: “Navalny’s team have released a list of names drawn up by Navalny just days before his returning arrest, which included Chelsea FC owner Roman Abramovich and … Alisher Usmanov.” Calling on the UK to target both with sanctions, Moran said: “Both individuals were described as key enablers with significant ties and assets in the west.” Labour’s frontbench was a little more cautious. Catherine West, a shadow Foreign Office minister, asked in the Commons: “Will the government commit to cleaning up the illicit money in UK jurisdictions including London,” which she said had been revealed in an intelligence and security committee report on Russia. Alyn Smith, the SNP’s foreign affairs spokesperson, said there was “considerable support in the house” for further sanctions against Russians, although he did not name individuals. Also named by Navalny was Andrey Kostin, the head of Russia’s state-owned VTB bank. Kostin, who was hit by US sanctions in 2018, is a frequent visitor to London. Kostin’s late son lived in the UK and worked for Deutsche Bank before returning to Moscow. Another person targeted by Navalny is Igor Shuvalov, a former first deputy prime minister and the chair of the state-run VEB bank. Shuvalov bought two flats worth £11.4m in Westminster, close to the Houses of Parliament. The properties are held via offshore trusts. A spokesperson for Abramovich said there was no foundation to Navalny’s claims. Usmanov has in the past reacted furiously to Navalny’s investigations into him, denying charges of political corruption. He successfully sued Navalny for libel over a video in 2017, and said in an online response: “Your attempts to slander me are like a puppy barking at an elephant.” Navalny was arrested on 17 January after flying back to Moscow from Berlin. He spent nearly five months in Germany recuperating from being poisoned with the nerve agent novichok. Navalny – who accuses Putin of trying to murder him – faces the prospect of years in jail on what he says are false charges.