The UK Government “clearly and unequivocally” recognises opposition leader Juan Guaido as president of Venezuela, lawyers representing Foreign Secretary Dominic Raab have told the Supreme Court.

The Foreign, Commonwealth and Development Office (FCDO) has intervened in a long-running case concerning around two billion US dollars (£1.45 billion) of assets belonging to the Venezuelan central bank.

Two “rival” boards of Banco Central de Venezuela (BCV) are battling to secure the release of over one billion US dollars (£800 million) of gold bullion held in the vaults of the Bank of England.

The two boards – one appointed by Venezuelan president Nicolas Maduro and another appointed by Mr Guaido – are also in a linked dispute involving around 120 million US dollars (£87.5 million) owed to BCV by Deutsche Bank.

Lawyers representing the “Maduro board” of the BCV took legal action last year to release the gold held on its behalf, which it wants to sell to help tackle the country’s coronavirus crisis.

But the Bank of England said it was “caught in the middle” of the rival claims to the gold, while the money owed to BCV by Deutsche Bank has been held by court-appointed receivers pending the outcome of the case.

At the centre of the high-stakes legal battle is who the UK Government recognises as the president of Venezuela: Mr Maduro or Mr Guaido.

In February 2019, the then foreign secretary Jeremy Hunt said the UK Government “now recognises Juan Guaido as the constitutional interim president of Venezuela, until credible presidential elections can be held”.

It is clear that one president, and one president only, is recognised.

The Government’s position was repeated in a letter from a senior FCDO official to a High Court judge considering the Deutsche Bank case in March 2020.

Last July, the High Court found Mr Hunt’s statement meant the Government “unequivocally recognised” Mr Guaido as interim president of Venezuela, and he therefore has the authority to give instructions in relation to the gold.

But, in October, the Court of Appeal said Mr Hunt’s statement was “ambiguous” and left open the possibility that the Government still recognises Mr Maduro as the “de facto” president of Venezuela.

Lawyers representing the Guaido board are appealing against that decision at a four-day Supreme Court hearing in London.

On Monday, lawyers representing Mr Raab told the Supreme Court that the FCDO’s letter to the court was “a clear and unequivocal recognition of Mr Guaido as president of Venezuela”.

Sir James Eadie QC, for the FCDO, said in written submissions: “It is clear that one president, and one president only, is recognised.”

He added: “The Foreign Secretary, on behalf of Her Majesty’s Government, hereby confirms that the UK recognised Mr Guaido as the interim president of Venezuela on February 4 2019 and continues to recognise him in that capacity.

“From that date, the UK no longer recognised Mr Maduro as the Venezuelan head of state, whether de facto or de jure.”

Timothy Otty QC, representing the Guaido board, said the Government’s intervention meant that the issue of who the UK recognised as the president of Venezuela must be decided “in our favour”.

He told the court: “Her Majesty’s Government recognises Mr Guaido and only Mr Guaido as president.”

But Nicholas Vineall QC, representing the Maduro board, said: “We do not at all accept that the statement or explanation given by the Secretary of State is fatal to the Maduro board’s case.

“Indeed, we suggest it supports the Maduro board’s case.”

The hearing, which is being held in person at the Supreme Court in London and livestreamed on the court’s website, is due to finish on Thursday and it is expected that judgment will be given at a later date.