A Russian IT specialist claims that he was asked by the Russian Security Service to provide back door access to the system issuing visas for Russians to travel to Britain.
The individual is currently seeking asylum in the United States, the BBC said.
He spoke initially to the Bellingcat investigative website who investigated his claim and published a report today.
The BBC has also spoken directly to the individual who has asked not be named to protect his safety.
While it is impossible to verify many of the details, experts say his story is consistent with activity by the Russian security services.
It is unclear if it is linked directly to the travel of Russian intelligence operatives to Salisbury this March when Sergei Skripal was poisoned.
The man – known as "Vadim", which is not his real name – worked for TLScontact, a company which provides IT services to consulates for visa applications. In the case of the British operation in Russia, it processes and transmits data to London where final decisions on visas are made.
While working for the company in China, Vadim got married and when he was posted back to Moscow in late 2015 he encountered problems in getting his family back with him.
He believes that along with the harassment of other members of his family in Russia, this was part of a ploy by the Russian Security Service – the FSB – to try to get him to collaborate with them.
In April 2016 he said he was approached by someone who offered to make the problems go away. He was asked to co-operate with the FSB and signed a document indicating that. He says the individual said they wanted information on the operations and IT network of TLScontact including a "network map".
Vadim claims he complied with requests and soon after noticed intrusions into the IT system. Further meetings and requests followed. Vadim claims he then made a series of attempts to leave Russia but was stopped and warned.
He was also asked to report on visa applications of certain people of interest. He believes the access would have allowed the FSB to monitor the flow of information and analyse the patterns of successful applications in order to understand better how to secure visas as well as gather personal information of those applying.
He says he was eventually asked to create an electronic "backdoor" allowing access to the visa centre network of the British consulate. He believes the type of access that the FSB was trying to engineer might allow them to potentially monitor details provided in Russia and intercept the details being transferred between Russia and the UK.
Vadim claims he got his family out of the country at this point and then left Moscow in September 2016 without carrying out the request. He travelled to the U.S. and requested political asylum.
He says he tried contacting a public hotline for MI6 when he arrived in the U.S. but never heard back. He also says he contacted a person in the British embassy in Moscow but with no response as was the case when he tried to contact TLScontact.
In March 2018, two operatives of Russian military intelligence (the GRU) are alleged by Britain to have come to the UK to poison Sergei Skripal with Novichok nerve agent.
They travelled on valid visas. There is no direct evidence linking their applications to any subversion of the visa system in Russia. Officials in the UK have suggested they received legitimate visas based on the false documentation including passports they provided and have played down any possibility that the system was subverted.
Vadim's claims do suggest there is a long standing interest in attempting to monitor, track and potentially subvert the process of issuing visas for individuals from Russia trying to come to the UK.
It is impossible to verify all of his claims but Western security sources say they are consistent with the behaviour and activity they would expect from the FSB.
The Bellingcat organisation – which has conducted numerous investigations of Russian activities – say they have seen further documentation which they say supports the story. The Home Office in London says that the ultimate decision for the issuing of a visa is in London and does not rest with the contractor.