Sir Keir Starmer said Britons should not panic over the economic impact of the Iran war but acknowledged people might have to change their shopping habits and holiday plans.
The prime minister, who will lead a meeting of the ministerial Iran crisis committee on Tuesday, said “at the moment” the government was confident about supply chains.
He said the UK was doing “everything we can” to reopen the Strait of Hormuz, the vital oil and gas shipping route which has been effectively closed by Iran since the US-Israeli bombing campaign began.
Sir Keir said the French and the British would lead a “military mission” to provide reassurance to ships passing through the strait, although the initiative, driven by the prime minister and French president Emmanuel Macron, is not expected to begin until hostilities cease.
Sir Keir told the Cathy Newman Show on Sky News: “There is going to be an impact on the UK. There already is.
“And I think it’s really important that I level with the public that we are doing everything we can to get the Strait of Hormuz open, because obviously that is vital in terms of minimising the impact.
“But I don’t want anybody to think that, once the Strait is open, that that’s the end of the damage. It will go on longer than that.”
He said there were “almost daily meetings” of ministers and officials looking at how to manage the impact of the crisis.
“At the moment, we’re confident about supply. We have reopened a CO2 plant in the North East. Airlines are telling us that they’ve got enough jet fuel at the moment.”
But he added “we’ll see how long the conflict goes on”.
He said: “I can see that, if there’s more impact, people might change their habits… where they go on holiday this year, what they’re buying in the supermarket, that sort of thing.”
Asked for his message to the public, Sir Keir said: “Don’t panic.
“But, we chose not to get involved in this war. That was the right thing to do but we must protect the British people from the impact of it.”
Tuesday’s meeting of the Middle East Response Committee (Merc), the panel set up to deal with the fallout from the crisis, will be attended by senior ministers and representatives from the Bank of England.
Earlier, in a speech in Lancashire, the prime minister said the response to the economic and political shock from the war, which has strained transatlantic relations with president Donald Trump’s US, “will define not just this government but arguably this generation”.
Sir Keir said: “The world has changed. It is more volatile and dangerous now than at any other point in my lifetime.”
Oil prices hit a near three-week high on Monday, as hopes of progress on peace talks between the US and Iran were once again dashed.
Negotiations had been expected to take place in Pakistan before Mr Trump declared over the weekend that envoys from Washington would no longer be travelling to Islamabad because of a lack of progress with Iran.
Mr Trump told Fox News on Sunday: “If they want, we can talk but we’re not sending people.”
He last week indefinitely extended the ceasefire between the US and Iran, which was agreed on 7 April and which has largely halted the fighting that began with joint US and Israeli strikes on 28 February.
But a permanent resolution has yet to be agreed and the crucial Strait of Hormuz, through which a fifth of the world’s shipped oil supplies are carried, remains effectively blocked.
Oil prices fell in mid-April when it appeared that progress was being made towards reopening the strait, but Mr Trump’s announcement at the weekend has sent prices soaring again.
The cost of benchmark Brent crude continued its ascent, rising 2 per cent to around 108 US dollars a barrel on Monday, back up to levels seen before the first round of peace talks began in early April.
Sir Keir reiterated that the government had capped household energy costs until July, regardless of what happens in Iran, while fuel duty is scheduled to remain frozen until September.
