Concerns have been raised by MI6 over a Russian oligarch, who has connections to Vladimir Putin, capitalising his controversial business on the London Stock Exchange.
The Telegraph has reported that the security services raised red flags after they questioned why they were not informed when a Putin-linked energy company was floated on the LSE last year.
The firm in question is EN+, which is controlled by billionaire Oleg Deripaska who has close links to the Russian president.
The firm also owns half of Rusal, an aluminium company that used to produce military-grade equipment.
It is thought that some of the company's technology went into the Russian-built Buk missile that Dutch investigators believe destroyed Flight MH17 over Ukraine in 2014, killing 298 people on board.
The former defence minister, Sir Mike Penning, has penned a series of questions for the House of Commons about the issue including whether the flotation represented "a threat to the UK's national interests and security".
EN+ has more controversial connections in that it is partly controlled by the Russian-state owned bank, VTB.
The bank is subject to joint EU-US sanctions but is thought to have spent £697m to help fund the flotation.
EN+ Group raised $1.5bn (£1,1bn) from international investors, valuing the company at $8 billion for the flotation to go ahead.
A source told the Telegraph that neither MI6 nor the National Security Council had been consulted about the flotation.