In the recording, an officer of Iran’s Islamic revolutionary guard is heard telling the Stena Impero to change course, adding: “You obey, you will be safe.”
The audio released Sunday by Dryad Global shows how the British Navy was unable to prevent the ship's seizure by Iranian forces on Friday.
The British officer is heard saying that the transit of the vessel must not be impaired under international law.
Iran’s Guard seized the Stena Impero and another British oil tanker in the Strait of Hormuz on Friday over what it claimed were violations of international regulations.
The incident happened at around 4pm UK time. The Stena Impero, “was approached by unidentified small crafts and a helicopter during transit of the Strait, while the vessel was in international waters”, according to the tanker’s owners, Stena Bulk.
Britain has called Iran’s capture of the Stena Impero in the Strait of Hormuz on Friday a “hostile act”.
The port authority chief was quoted by the semi-official Tasmin news agency, as saying that it was “causing problems”.
But the incident comes after tensions between the US, the UK and Iran flared up, and Iranian officials say the move came in response to Britain’s role in seizing an Iranian supertanker loaded with some 2 million barrels of crude oil weeks earlier.
Days later, Iranian boats tried to impede a British oil tanker before being seen off by a Royal Navy frigate in the Strait of Hormuz.
Britain sent a second warship, HMS Duncan, to the Persian Gulf after the incident.
The escalation of tension comes after Donald Trump unilaterally withdrew the US from a 2015 deal, which saw Iran curtail its nuclear programme in exchange for normalised economic relations, and tightened restrictions on trade with Iran.
Other world powers have tried to salvage the deal, but Iran has begun a new uranium enrichment programme in response to the lack of economic benefits.
Agencies contributed to this report.