Conservative MPs have tabled an amendment to Labour's immigration legislation that would force the Home Office to remove visa sponsor licences from any individual or company under UK sanctions. The move follows the discovery that firms linked to the Russian and Iranian regimes had been approved to sponsor workers to come to Britain.

Shadow security minister Alicia Kearns warned that Labour was leaving Britain's backdoor “open to immigration sponsored by our enemies”. “Sanctions are supposed to punish those who threaten our national security and undermine our interests,” she said. “It is therefore utterly absurd that a company can be sanctioned by Britain and still bring in workers to our country.”

Shadow home secretary Chris Philp said the Conservatives would close the loophole. “We will not allow sanctioned firms from Russia or any country to import people to our country and put our safety at risk,” he said.

The amendment comes after an investigation earlier this year found that four sanctioned companies appeared on the Home Office's Register of Licensed Sponsors (Workers), published on 3 July. They were Russia's national airline Aeroflot, cryptocurrency platform Exmo Exchange, and two Iranian state-owned lenders, Bank Melli and Persia International Bank. All four were rated ‘A’ for compliance, meaning they could issue certificates of sponsorship allowing workers to apply for visas, including under the Skilled Worker route. The investigation was reported in July.

The Government has said no skilled worker visas were issued by the companies after they were sanctioned, and that their activities remain regularly reviewed. The two Russian companies are no longer on the sponsor list, The Sun reported.

A Home Office spokesperson said the power to revoke sponsorship from sanctioned companies already exists. The department points to the scale of the sanctions regimes: the UK has now sanctioned more than 3,500 individuals, businesses and ships under the Russia sanctions regime, and more than 550 individuals and entities under the Iran sanctions regimes, including the Islamic Revolutionary Guard Corps in its entirety. See the UK Sanctions List on GOV.UK.

A sponsor licence is the gateway through which employers bring overseas workers to Britain: without one, a firm cannot issue the certificates of sponsorship that workers need to apply for a visa. Losing a licence therefore cuts off a company's ability to recruit from abroad, which is why the question of whether sanctioned firms should hold one has become a test of how seriously the sanctions regime is enforced.

The amendment would turn a discretionary power into a duty, requiring the Home Office to act whenever a sponsor is sanctioned. It is a proposal at this stage: it would need to be accepted and passed through Parliament before it could become law, and no vote date has been reported. The rules on sponsor licences can change, so employers and workers should check the official GOV.UK guidance for the current position.