The UK will seek to organise a European-led naval contingent for the Gulf to escort ships following an “act of state piracy” by Iran in seizing a British tanker.

Jeremy Hunt told the Commons that discussions have taken place with a number of allied states in the last 48 hours on the forming of a protection force with further talks to be held later this week.

The foreign secretary said: “It is with a heavy heart that we are announcing this increased international presence in the Gulf because the focus of our diplomacy has been on de-escalating tensions in the hope that such changes would not be necessary.”

But, he said, Tehran had flagrantly flouted the law in capturing the Stena Impero in international waters.

The move is certain to further escalate tensions between Britain and Iran which began when royal marines boarded an Iranian owned tanker, Grace 1, off the coast of Gibraltar for allegedly smuggling oil to the Assad regime in Syria in breach of European Union sanctions.

Tensions high as Trump approves new Iran sanctions: In pictures Show all 17 1 /17 Tensions high as Trump approves new Iran sanctions: In pictures Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, their surface-to-air missile is seen as it shoots down a US surveillance drone EPA Tensions high as Trump approves new Iran sanctions: In pictures This photo shows US RQ-4A Global Hawk unmanned surveillance drone. A drone of this model was shot down by Iran on Thursday 21 June AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures An oil tanker is on fire after it was subject to a suspected attacked at the Gulf of Oman on June 13. The US has blamed Iran for the attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures US President Trump holds up a signed executive order to increase sanctions on Iran on 24 June AP Tensions high as Trump approves new Iran sanctions: In pictures Iranian President Rouhani stated in a televised address that the White House is "afflicted by mental retardation" following the increase in sanctions on 25 June EPA Tensions high as Trump approves new Iran sanctions: In pictures An Iranian navy boat tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Iran claims that in this picture released by Iran state TV, debris from the downed US drone is seen after it was recovered from Iranian waters AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures A screenshot from a video released by the US Department of Defense that the US claims to show Iranian removing an unexploded limpet mine form the hull of the Japan-owned ship that was attacked in the Gulf of Oman on June 13 Getty Tensions high as Trump approves new Iran sanctions: In pictures An item reportedly found on the Japan-owned oil tanker that was attacked on June 13 in the Gulf of Oman AFP/Getty Tensions high as Trump approves new Iran sanctions: In pictures A handout photograph from the US Department of Defense shows a composite material that the US claim was left behind on the hull of the Japan-owned oil tanker following the removal of an unexploded limpet mine Getty Tensions high as Trump approves new Iran sanctions: In pictures A view from the cabin of an Iranian navy boat as it tackles the fire on the Norwegian owned Front Altair oil tanker after it was hit in a suspected attack EPA Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The picture suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack Reuters Tensions high as Trump approves new Iran sanctions: In pictures Smoke billows from an oil tanker after it was subject to a suspected attacked at the Gulf of Oman on June 13 Reuters Tensions high as Trump approves new Iran sanctions: In pictures Release by US government A picture released by U.S. Central Command shows damage to the hull of the oil tanker Kokuka Courageous. The pictures suggests that the ship is 'likely' to have been hit by a mine as the US Secretary of State Mike Pompeo moves to blame Iran for the suspected attack EPA

No EU state had seized a ship using force in seas over a sanctions breach before and Tehran accused London of acting on US instructions.

But Jeremy Hunt told MPs that Iran “had no right to obstruct the ship’s passage, let alone board her” under international law.

“It was therefore an act of state piracy. We will now seek to put together a European-led maritime protection mission to support safe passage of both crew and cargo in this vital region,” he said.

“If Iran continues on this dangerous path, they must accept the price will be a larger western military presence in the waters along their coastline, not because we wish to increase tensions but simply because freedom of navigation is a principle which Britain and its allies will always defend,” he added.

Fabian Hamilton, the shadow minister for peace, warned of a “tit-for-tat cycle of actions”. The Labour minister questioned why a British-flagged tanker was “left so hopelessly unprotected in the Strait of Hormuz” when anyone with any understanding of the issue could see that “this was exactly” how Iranians would respond following the seizure of one of their tankers.

However, Mr Hamilton added: “Iran’s actions in recent weeks in the Strait of Hormuz have been utterly unacceptable and should be condemned from all sides.”

The UK Chamber of Shipping backed the foreign secretary with Bob Sanguinetti, the chief executive officer, saying: “We welcome the announcement of a joint European maritime mission to protect British and European interests in the Strait of Hormuz.

“While the European maritime mission is a step in the right direction, It is imperative that the UK government continues to protect the interests of British-flagged ships in the Gulf while the mission is assembled. This means formulating a mechanism that will provide confidence and security to allow ships to pass through the straits safely and securely. We continue to work closely with government to achieve this,” he added.

The foreign secretary’s announcement came on a day in which Iran announced that it has arrested “17 spies” for working for the CIA, with some sentenced to death. The intelligence ministry in Tehran claimed the suspects had been collecting information on nuclear, military and other sectors. Donald Trump said the allegations were “totally false”.

The Iranian authorities also released images of crew members on board the Stena Impero showing Iranian officials talking to them and meals being prepared.

Crew members of the British-flagged tanker ‘Stena Impero’ seen in an image released by Iranian state media (EPA)

The majority of crew are Indian and the Iranian embassy in India said they were in good health and were being well looked after. The crew of the Iranian tanker being held in Gibraltar are also predominantly Indian. Delhi was one of the main purchasers of Iranian oil before the Trump administration imposed new sanctions.

Some Iranian officials have been of the view that the UK may start to take a tougher line with Tehran, especially with the imminent expected arrival of Boris Johnson in Downing Street, and hawks in the US administration may try to bring their influence to bear.

Despite his frequent tirades against Iran, President Trump aborted planned military strikes after attacks on two oil tankers in the Gulf earlier this year. He has also given Senator Rand Paul, who has been a steadfast opponent of America’s wars abroad from a right-wing libertarian stance, a role in negotiating with Iran.

The Kentucky senator is being viewed as a counterweight to the president’s national security advisor, John Bolton, who has been a serial advocate military intervention and has, in the past, called for regime change in Tehran.

The Iranian foreign minister, Mohammad Javad Zarif, appeared to think there is a risk of a Boris Johnson government becoming susceptible to pressure from the American hawks. He tweeted on Monday: “Having failed to lure @realDonald Trump into War of the Century, and fearing collapse of his #B Team, @AmbJohnBolton is turning his venom against the UK in hopes of dragging it into a quagmire. Only prudence and foresight can thwart such ploys.”

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While the Trump administration has tried to dismantle the Joint Comprehensive Plan of Action (JCPOA), reached between international powers and Iran over its nuclear programme, the other signatories – Britain, France, Germany, Russia and China – had sought to keep it going. The European states are seeking to set up a payment mechanism under which businesses can continue trading with Iran, circumventing US sanctions.

Before Mr Hunt’s statement to the Commons, an Iranian official told The Independent: “We have complained that the others [nuclear deal signatories] have not done enough to protect the JCPOA, but we accept that they, including the UK, see that it should be kept going.”

“On the tankers we are unhappy with the UK about what happened in Gibraltar. But there was good dialogue. What we are worried about is whether this would change with Britain trying to show its loyalty to America,” the official added.

Earlier in the day in London, Theresa May chaired her last Cobra meeting and her spokesperson rejected claims that it had rejected a US offer to escort British ships through the Gulf. A spokesperson said: “There has never been a US offer that has involved them escorting all UK ships. The US has been discussing with a number of countries, including the UK, how we might deliver maritime security in the face of recent threats to shipping.”

As for Washington, secretary of state Mike Pompeo said on Monday when asked about the tanker, that “the responsibility ... falls to the United Kingdom to take care of their ships”.

Downing Street also sought to refute charges that the royal navy had been so denuded by cuts in the 2010 Strategic Defence and Security Review that it had failed to protect UK vessels from Iranian gunboats. “We always said that we will ensure we have all the capability that we need in order to protect the UK and serve its interests. We have the largest military budget in Europe. We are investing in a world-class royal navy”, the spokesperson said.