Iran has previously proposed that the detained vessels could be swapped, but the offer was this morning rejected by Dominic Raab, who was appointed foreign secretary after Johnson entered Downing Street on Wednesday.
Speaking to BBC Radio, Raab said: “There is no quid pro quo.
“Grace 1 was intercepted because it was in breach of sanctions and heading with oil to Syria.
“The Stena Impero was unlawfully detained. So this isn’t about some kind of barter.
In turn, Iranian Ambassador to the UK Hamid Baeidinejad also rejected the possibility of exchange of tankers.
“Impossible to advance a quid pro quo or barter exchange of detained UK and Iranian ships as some British media suggest. UK has illegally detained the ship carrying Iranian oil while the British ship is detained for violating some key safety/security regulations in Hormoz Strait,” the Iranian ambassador tweeted.