DO NOT follow Donald Trump into another illegal war of regime change, Prime Minister Keir Starmer was told by MPs and campaigners today.

As the US president continued to consider joining Israel’s aggression against Iran, there were growing fears that Sir Keir could repeat Tony Blair’s criminal blunder of 2003 when Labour joined the attack on Iraq.

Mr Trump could well ask the PM for British assistance, in particular through the use of the military base at Diego Garcia in the Indian Ocean.

It is believed that Downing Street has been told by Attorney-General Richard Hermer that any such participation in the war would breach international law.

While No 10 declined to comment on his advice, an official who has seen it told the Spectator magazine that the attorney-general “has concerns about the UK playing any role in this except for defending our allies.”

This week, Defence Secretary John Healey dispatched extra fighter aircraft to the region, allegedly to help “de-escalate” the crisis.

Independent MP Jeremy Corbyn told the Star: ”Israel’s unprovoked military attack on Iran is totally illegal in international law.

“Just remember: the world could have stopped the genocide in Gaza. Instead, governments — including our own — allowed Israel to act with total impunity.

“Israel’s reckless strikes on Iran are the product of that impunity. It is time our government woke up, ended its complicity in Israeli war crimes and, for once, stood up for international law.”

Stop the War Coalition convener Lindsey German warned: “There must be no temptation to follow the US into an illegal war.

“You cannot seriously make the case that Israel is defending itself when everyone, even Trump advisers, are saying there is no Iranian nuclear bomb and many of his supporters are extremely worried.

“Every attempt at regime change in the Middle East in the last 25 years has been a disaster.

“The US and the UK would be following a man, [Israeli PM Benjamin] Netanyahu, who has led a genocidal war against the people of Gaza. What moral or legal authority would we have if we did?”

And Workers Party leader George Galloway, a central figure in the 2003 anti-war campaign, told the Star: “The very same playbook, the very same tropes — from both conservative and liberal mouthpieces — as 2003.

“Except this time they haven’t even bothered with a dossier! Another difference is that Iran, unlike Iraq, has plenty to fight back with. And China and Russia are in play in a way they were not in 2003.

“Netanyahu has bitten off more than he can chew. And even the glutinous Donald Trump may have difficulty with the US public finding the case for war hard to swallow.”

Senior Labour MP Diane Abbott added: “UK involvement in war with Iran will be just as disastrous as the war with Iraq.”

Liberal Democrat leader Ed Davey demanded that the government publish Mr Hermer’s advice.

“The last thing we need is for the UK to be dragged into another illegal war in the Middle East by the US,” he said.

Sir Keir, however, said that the “key principles” in the crisis were disarming Iran and protecting Israel.

“All of us, UK included, are very concerned about the nuclear programme that Iran is developing — we’ve long been concerned about that,” he said.

“Also, we completely recognise Israel’s right to self-defence, but the principle is that we need to de-escalate this.

“It’s already having an impact on the economy. Yes, the nuclear issue has to be dealt with, but it’s better dealt with by way of negotiations than by way of conflict.”

Foreign Secretary David Lammy was in Washington today for emergency talks with his US opposite number, Marco Rubio, potentially asking for the government to be let off the hook of a difficult decision by Mr Trump.

Chancellor Rachel Reeves offered a different, overtly imperialist explanation to Mr Healey for the British military deployments to the region.

“We always want to protect our interests, and so that’s why we’ve made those decisions to move those assets there, in the case of them being needed,” she said.

The Tories are lining up firmly for war, with shadow foreign secretary Priti Patel dismissing considerations of legality completely.

“I don’t think we can hide behind legal advice at a time of crisis and national security when we have to work alongside our biggest ally in the world, the United States,” she said.