A London-based firm is being investigated by the British authorities on suspicion of indirectly aiding North Korea's nuclear weapons programme, after it allegedly evaded UN sanctions on the dictatorship, The Telegraph can reveal.

Amet Ventures Ltd, which is registered at a St Paul’s address in central London, is suspected of helping to facilitate the sale of North Korean coal through Russian ports to beat UN sanctions.

The case illustrates how Kim Jong-un's secretive regime is now suspected of using an increasingly complex network of falsified documents, foreign traders and ship-to-ship transfers to bypass tough UN economic sanctions, such as the ban on coal sales.

“The UK is aware of the allegations regarding this UK registered company and law-enforcement agencies are investigating any evidence that indicates involvement in illicit sanctions activity. We cannot comment further whilst investigations are ongoing,” a UK Foreign Office spokesman said.

The UK-registered company, which has Ukrainian directors, denied it had been involved in any sanctions-busting activity, saying its identity had been appropriated by others.

"Our company strongly denies any allegation of wrongdoing," said Ievgen Moshkov, the firm's Ukrainian director, claiming in a statement to The Telegraph that the company's identity had been ‘pirated’ and used it to illegally export banned materials.