Labour leader Jeremy Corbyn has told the Government to stand up to the "belligerent actions and rhetoric" from the US after the nation killed Iran's top general.
Mr Corbyn described the assassination of Iranian general Qasem Soleimani as "an extremely serious and dangerous escalation of conflict in the Middle East".
He also called on all countries to "ratchet down the tensions to avoid deepening conflict".
General Qasem Soleiman was killed by a US air strike at Baghdad airport in Iraq ordered by United States President Donald Trump.
He was head of Tehran's elite Quds Force who spearheaded military operations in the Middle East.
In a statement, Mr Corbyn said: "The US assassination of Iranian general Qasem Soleimani is an extremely serious and dangerous escalation of conflict in the Middle East with global significance.
"The UK Government should urge restraint on the part of both Iran and the US, and stand up to the belligerent actions and rhetoric coming from the United States.
"All countries in the region and beyond should seek to ratchet down the tensions to avoid deepening conflict, which can only bring further misery to the region, 17 years on from the disastrous invasion of Iraq."
Mr Corbyn has previously been criticised in the past for his views on Iran.
According to his register of interests, Mr Corbyn was paid for appearances on the Iranian state broadcast network Press TV between 2009 and 2012.
The channel had its licence revoked by Ofcom in 2012 after the media regulator ruled that the state broadcaster's English language outlet had breached several broadcasting licence rules over editorial control of the channel.
Press TV also had a £100,000 fine imposed in 2011 after broadcasting an interview with imprisoned Newsweek and Channel 4 journalist Maziar Bahari, which Ofcom said had been conducted under duress.
Mr Corbyn has previously said he used the opportunity to appear on Press TV to raise the issue of human rights in Iran and around the world.
In June 2019, Mr Corbyn was branded "pathetic" by then foreign secretary Jeremy Hunt after he questioned whether the UK had "credible evidence" Iran was behind attacks on two oil tankers in the Gulf of Oman.
Mr Hunt accused Mr Corbyn of "virulent anti-Americanism" after he blamed Britain and the United States for stoking conflict with Iran.
