Rishi Sunak has said joint US-UK air strikes on Houthi targets in Yemen last week were intended as a “limited single action” but refused to rule out more of them.

After a further Houthi missile attack on a ship in the Red Sea  on Monday, the Prime Minister said his government was “prepared to back our words with actions”.

Updating the Commons on the military action, Mr Sunak said the UK would “not hesitate to protect our security, our people and our interests where required.”

Labour leader Sir Keir Starmer, who was briefed on Thursday’s strikes in advance, said his party backed “targeted action” provided it was “underpinned by a clear strategy”.

Complaining parliament hadn’t been recalled to debate the action, SNP Westminster leader Stephen Flynn said there was “an enormous question… as to what comes next”.

He said: “What is the plan? What is the Prime Minister’s strategy? 

“Will he… lay out when and how far he is willing to go in relation to military action, because quite clearly we need to understand his government’s strategy in this conflict. 

“We cannot have an escalation which leads to further regional instability.”

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Mr Sunak was speaking shortly after a missile struck a US-owned ship off the coast of Yemen, suggesting the air strikes had failed to curb the recent Houthi attacks.

A recent surge in attacks in the Red Sea, which is used by 15% of world shipping, has forced vessels to travel around the southern tip of Africa, adding thousands of miles to journeys, hiking fuel costs, and upending tightly planned logistics.

With prolonged disruption liable to hit the global economy and add to inflation, the US and UK struck 13 targets in Yemen in a bid to quell the Iran-backed Houthi attackers. 

The Houthis, who support Hamas in the Palestinian group’s war against Israel in Gaza, claim they have targeted ships with links to Tel Aviv.

But Mr Sunak said that was a “malign narrative” and urged people not to fall for it.

The Prime Minister told MPs: “I do not take decisions on the use of force lightly. That is why I stress that this action was taken in self-defence. It was limited, not escalatory.

“It was a necessary and proportionate response to a direct threat to UK vessels and therefore to the UK itself.

“The threats to shipping must cease. Illegally detained vessels and crews must be released. And we remain prepared to back our words with actions.

“Our initial assessment is that all 13 planned targets were destroyed. We have seen no evidence thus far of civilian casualties, which we took great care to avoid."

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He added: “We shouldn’t fall for their (the Houthis’) malign narrative that this is about Israel and Gaza. They target ships from around the world.

“And we continue to work towards a sustainable ceasefire in Gaza and to get more aid to civilians. We also continue to support a negotiated settlement in Yemen’s civil war.

“But I want to be very clear that this action is completely unrelated to those issues.

“It is a direct response to the Houthis’ attacks on international shipping.”

Sir Keir added: “We strongly condemn the Houthi attacks that are targeting commercial ships of all nationalities, putting civilians and military personnel in serious danger - including British forces.

“The Houthi attacks are unacceptable, illegal and, if left unaddressed, could lead to a devastating rise in the cost of essential food in some of the poorest countries. The international community clearly stands against the Houthi attacks.”

He urged Mr Sunak to bring any further military action to the Commons, saying “scrutiny is not the enemy of strategy” and it was vital to “avoid escalation across the Middle East”.

Mr Sunak assured him it had been “necessary to strike at speed” to protect operational security.

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Urged by several Tory MPs to ramp up defence spending, Mr Sunak said his intention was to raise it to 2.5% of GDP "when circumstances allow".

Defence Secretary Grant Shapps also refused to rule out the UK joining further strikes, telling Sky News: “If we have to take further action, that is something that we will consider.”

Speaking later in London, he said the allies’ aim was to “de-escalate tensions in the region” after commercial shipping and a Royal Navy warship were attacked.