Sir Keir Starmer and Emmanuel Macron will meet international counterparts this week for talks on reopening the strait, which has been closed by Iran.
The UK and France are leading political and military planning to reopen the Strait of Hormuz, but no mission will begin until hostilities between the US and Iran end, Sir Keir Starmer said.
The Prime Minister was speaking after Donald Trump’s blockade of Iranian ports came into effect, with the US president threatening to sink Tehran’s fast attack vessels if they come near American warships.
Sir Keir refused to back Mr Trump’s blockade and called for unfettered access to the strait, a vital route for global oil and gas supplies from the Gulf.
With French President Emmanuel Macron, he said he was working to bring together an international coalition prepared to contribute to an initiative to secure freedom of navigation in the strait.
The Prime Minister told MPs the summit of world leaders later this week would focus on diplomatic efforts to reach a “negotiated end to the conflict” and the reopening of the strait, which had become a “running sore” to the world.
The leaders would also carry out military planning “to provide assurance to shipping as soon as a stable environment can be established”.
He said: “This is about safeguarding shipping and supporting freedom of navigation once the conflict ends.”
Mr Macron said: “This strictly defensive mission, separate from the warring parties to the conflict, is intended to be deployed as soon as circumstances permit.”
No effort must be spared to swiftly reach, through diplomatic means, a strong and lasting settlement to the conflict in the Middle East.
Such a settlement must provide the region with a robust framework enabling all to live in peace and security.…
— Emmanuel Macron (@EmmanuelMacron) April 13, 2026
Oil prices jumped back up to about the 100 US dollars (£74) a barrel mark after US talks with Iran broke down and Mr Trump made his threat to prevent ships leaving from 3pm on Monday.
Writing on his Truth Social platform, he said if any of Iran’s “fast attack ships” come close to the US blockade “they will be immediately eliminated”.
Mr Trump, who has repeatedly boasted about sinking the Iranian navy, said the smaller vessels had escaped destruction so far “because we did not consider them much of a threat”.
In his Commons statement, Sir Keir:
– Said Mr Trump was “wrong” to threaten to wipe out Iran’s civilisation.
– Acknowledged the “significant” economic consequences of the Iran war “will last longer than the conflict itself”.
– Demanded an end to Israeli bombing of Lebanon, saying the attacks were having “devastating humanitarian consequences”.
Ahead of his Commons appearance, Sir Keir told BBC Radio 5 Live: “We’re not supporting the blockade.”
He said: “What we’ve been doing over the last few weeks, and this was part of what I was discussing with the Gulf states last week, is bringing countries together to keep the strait open, not shut.”
Iran has selectively let through some vessels, but Mr Trump’s blockade is intended to stop that, in order to prevent Tehran from benefiting from tolls levied on shipping and the revenues from oil exports.
Mr Trump said “no-one who pays an illegal toll will have safe passage on the high seas”.
Mohammad Bagher Qalibaf, the parliamentary speaker who led Iran’s side in the negotiations with the US, said: “If you fight, we will fight.”
The rising cost of oil has already pushed up forecourt prices for motorists and added expenses to businesses, while households face a nervous wait to see what impact the turbulence will have on domestic electricity and gas bills when the price cap expires at the end of June.
The Resolution Foundation think tank has suggested the average working-age household could be £480 worse off this year as a result of the war.
Sir Keir said: “I’m very concerned about the impact that this war is having on people back in the United Kingdom who’ve obviously played no part in the war, but I don’t want them paying the price.
“So that’s my primary focus.”
Asked if Mr Trump was to blame for the economic hit caused by the war, Sir Keir said: “In terms of where the blame lies, it’s Iran that has caused the restriction on traffic and vessels through the Gulf, and they’re doing that in breach of international law.”
