The UK Government said it won’t approve the sale of North Sea oil and gas fields to an investment fund backed by Russian billionaire Mikhail Fridman.

The 12 oil and gas fields are owned by German utility RWE and the deal to buy them would be part of LetterOne’s (L1) acquisition of Germany’s oil firm DEA.

Mr Fridman’s company L1 Energy is said to have agreed to a €5 billion (£3.6bn) deal with RWE last year but its completion has been slowed by regulators’ concerns.

“If the proposed acquisition were to proceed in its current form, [Energy Secretary Ed Davey] would be minded to require the companies to arrange for a further sale to a suitable third party,” DECC said in a statement.

It added the Energy Secretary is responsible for “ensuring the continued and safe production of the UK’s petroleum resources”.

“In the discharge of these regulatory responsibilities, the Secretary of State has raised concerns with the respective companies about the effect that possible future sanctions imposed on LetterOne may have on the continued operation of these 12 fields and the serious health and safety and environmental risks that may result”, the statement said.