The Labour leader tweeted: “The UK tanker under Iranian control, and its crew, must be released. Escalation risks a deeper conflict, all sides must show restraint.
The Stena Impero, a Swedish-owned oil tanker sailing under a UK flag was boarded by Iran’s Revolutionary Guards on Friday and then forced to sail into Iranian territory.
Penny Mordaunt, the defence secretary, has said the vessel was in Oman’s territorial waters at the time it was seized and described Iran’s actions as a “hostile act”.
Earlier today John McDonnell, the Labour shadow chancellor and Mr Corbyn’s closest political ally, said the Iranian government was “obviously to blame for taking the tanker, it’s unacceptable behaviour and we echo what the Government has said”.
But his leader has taken a different approach to the growing diplomatic crisis and has instead laid the blame at the US government’s door.
Mr Trump decided to withdraw America from the nuclear deal with Iran last year, and instead ramped up sanctions on Tehran.
Many analysts believe Iran captured the Stena Impero in retaliation for Britain impounding Grace 1, an Iranian oil ship which was detained by Royal Marines off Gibraltar.
The British government has alleged the ship was on its way to deliver fuel to Syria, breaching EU sanctions.
A spokesman for Iran’s highly influential Guardian Council has been quoted describing Britain’s detention of Grace 1 as part of an “illegitimate economic war” and therefore Iran’s response in seizing the Strena Impero was part of “the rule of reciprocal action... well-known in international law”.
However, Iran’s increasingly aggressive action in the Gulf has also targeted US ships and included the Revolutionary Guards shooting down a US drone last month.
In an effort to pressure the Iranian regime, a senior diplomat has been summoned to the Foreign Office and Jeremy Hunt, the foreign secretary has “expressed extreme disappointment” in a phone call with his Iranian counterpart Javad Zarif.
Mr Corbyn has in the past been accused of being soft on Iran, with some critics pointing to his years spent presenting and contributing to programmes on Press TV, an English-language channel run and funded by Tehran.
Last month he cautioned against rushing to blame Iran for a spate of attacks on oil tankers in the Gulf without first gathering “credible evidence” of their culpability.
His remarks came after the Foreign Office said it was “almost certain” the Islamic Revolutionry Guard Corps, the hardline Islamist element of Iran’s armed forces, were behind the attacks.
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