Sir Keir Starmer said the UK would not get dragged into the Iran war as he refused to support Donald Trump’s blockade of the Strait of Hormuz.
The US president threatened to stop tankers from entering or leaving the key oil and gas shipping lane in response to the failure of talks with Iran, a move which has again caused global prices to spike.
The Prime Minister said “we are not supporting the blockade” as he repeated calls to fully reopen the strait, which has been effectively shut by Iran in response to the US-Israeli bombing campaign.
Speaking to BBC Radio 5 Live, Sir Keir 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.”
He said: “We’re not supporting the blockade and all of the marshalling diplomatically, politically and capability – we do have mine-sweeping capability, I won’t go into operational matters, but we do have that capability – that’s all focused, from our point of view, on getting the strait fully open.”
The American leader said on his Truth Social platform that the US military would start “blockading any and all ships trying to enter, or leave, the Strait of Hormuz” from 10am US Eastern Time, 3pm in the UK.
Mr Trump said “other countries will be involved with this blockade” and he told Fox News “the UK and a couple of other countries are sending mine sweepers” to the strait, and “it won’t take long to clean it out”.
But Sir Keir said: “My decision has been very clearly that whatever the pressure – and there’s been some considerable pressure – we’re not getting dragged into the war. The UK is not getting dragged in.
“That’s not in our national interest, because I’m not going to act unless there’s a clear, lawful basis and a clear thought-through plan.”
The UK and France are set to organise a conference with countries willing to contribute to a “peaceful multinational mission” to restore freedom of navigation in the strait, Emmanuel Macron said.
The French president said: “This strictly defensive mission, separate from the warring parties to the conflict, is intended to be deployed as soon as circumstances permit.”
Oil benchmark Brent crude jumped back past 100 US dollars a barrel, rising by more than 7% to 102 dollars in Monday morning trading and sparking fears of a worsening global energy crisis.
Stock markets also fell on Monday on fading hopes of a resolution to the Middle East conflict, with the FTSE 100 Index down 0.5% or 47.3 points lower at 10553.2 in early trading and the Dax in Germany and France’s Cac 40 both more than 1% lower.
The rising cost of oil has already pushed up forecourt prices for motorists and added expense 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.”
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
Iran has selectively let through some vessels but Mr Trump’s blockade is intended to stop that in order to prevent Tehran 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” in the announcement made after talks between the US and Iran broke down.
The US military will blockade Iran’s ports and coastal waters under the policy but Tehran has vowed to retaliate.
Mohammad Bagher Qalibaf, the parliamentary speaker who led Iran’s side in the talks, said: “If you fight, we will fight.”
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