Monitoring

“The UK Government is concerned by this action and we urge the Iranian authorities to de-escalate the situation.”

The Prime Minister’s spokesman said: “We are continuously monitoring the security situation there and are committed to maintaining freedom of navigation in accordance with international law.” The Revolutionary Guard Corps claimed the clash did not happen and Iran’s foreign minister Mohammad Javad Zarif dismissed the British account as “worthless” and intended to “create tension”.

The stand-off comes amid high tension between the US and Iran over a 2015 nuclear deal, from which US president Donald Trump withdrew last year. Last month, two tankers were damaged by explosions in the Gulf of Oman, which the US blamed on Iran.

Yesterday, former Royal Navy chief Lord West of Spithead urged the UK to speed up the building of more frigates.

The Labour peer warned the House of Lords that the lack of frigates “makes us less secure. It means wars are more likely and it’s really important to move forward”. He said out of 13 frigates, only eight were effectively available for operations by this “great maritime nation of ours”.

The nearest major warship to the one in the Gulf was “the other side of Suez, which I find rather worrying”, he added.

Defence minister Earl Howe said HMS Montrose had demonstrated that “we have the right assets in the right places” and told peers the priority was to reduce tensions in the region.

He said ministers remained committed to a surface fleet of at least 19 frigates and destroyers, adding: “The Royal Navy will have the ships it requires to fulfil their policy commitments.”

Meanwhile, Gibraltar police arrested the captain of the Iranian Grace 1 supertanker said to be delivering oil to Syria. They said: “The investigation is still ongoing and the Grace 1 continues to be detained.”