In November, MPs on Parliament’s Treasury Select Committee quizzed OFSI officials about the effectiveness of their investigations, but officials said the NCA was the body ultimately responsible for prosecuting and convicting those found to have breached the rules.

In a subsequent letter to the committee’s chair, the NCA’s Director-General, Graeme Biggar, pointed to the “complex and lengthy” nature of the cases.

He said that similar cases in comparable countries took an average of seven years to be completed.

The Sanctions and Anti Money Laundering Act, which is the legislation used to bring prosecutions, was only introduced four years ago.

Mr Biggar said: “Financial investigations of this nature are typically complex and lengthy. As a result, there have been no concluded prosecutions for offences under the new Sanctions and Anti Money Laundering Act.”

He added that the NCA had a “number of ongoing investigations with respect to financial sanctions breaches and other relevant crimes, some of which are awaiting charging decisions”.

In February last year, the NCA did bring charges against the former governor of a Crimean city, who was charged with seven counts of circumventing sanctions and two of money laundering.

Treasury Select Committee chair Dame Meg Hillier said it was “critical the government can demonstrate that there are consequences when sanctions are breached”.

She added that “we must maintain the pressure on Russia-linked organisations and ensure there is a clear deterrent which prevents anyone from attempting to circumvent sanctions against Russia”.

In November, David Lammy said Western sanctions had “deprived Russia of more than $400 billion since February 2022, which is equivalent to four more years of funding for the invasion”.

When asked by MPs whether he would be taking action against UK companies helping facilitate the Russian oil industry, he said, “There is more to come, I suspect, over the coming days.”

It is understood that no such action has yet been taken, but the government did appoint former Labour MP Baroness Margaret Hodge as an anti-corruption champion in December.