MI6 has raised concerns after a Russian oligarch with links to military hardware production was able to use the London Stock Exchange to raise an estimated £1 billion.

Security sources have raised questions over how EN+, an energy company, came to be floated in London last November without the intelligence services being properly consulted.

EN+ is controlled by Oleg Deripaska, one of Russia’s wealthiest men who is closely linked to Vladimir Putin.

The company also owns half of Rusal, a giant Russian aluminium company which until recently said on its website that a fine metal powder it produced was used “in the production of military equipment”. Mr Deripaska is president of Rusal.

The Telegraph understands that the same type of powder was used in the production of a Russian-built Buk missile that Dutch investigators said downed Flight MH17 over Ukraine in 2014, killing 298 people.