Rishi Sunak has said the UK would not hesitate to launch further air strikes against the Iran-backed Houthi rebels if attacks on shipping continued.
Royal Air Force jets took part in a second wave of joint US-UK action against the Yemen-based rebels on Monday night after attacks on shipping in the Red Sea and Gulf of Aden continued.
The Prime Minister told MPs: “We are not seeking a confrontation. We urge the Houthis and those who enable them to stop these illegal and unacceptable attacks.
“But, if necessary, the United Kingdom will not hesitate to respond again in self defence.
“We cannot stand by and allow these attacks to go unchallenged. Inaction is also a choice.”
Four RAF Typhoons and a pair of Voyager tankers were involved in the latest action.
Several targets were hit at two military sites north of Yemen’s capital Sanaa.
Mr Sunak said the strikes were aimed at sites which the Houthis use to support the attacks on shipping and “all intended targets were destroyed”.
A summary of the Government’s legal position said the UK is permitted under international law to use force “in such circumstances where acting in self-defence is the only feasible means to deal with an actual or imminent armed attack”.
The Houthis have been targeting shipping they claim is linked to Israel in the context of the conflict with Hamas.
But the UK and allies have warned the attacks are indiscriminate and have included targeting Royal Navy and allied warships.
The Red Sea route leading to and from the Suez Canal is one of the world’s most important shipping routes and there are concerns that the cost of diverting vessels away from it, around southern Africa, will fuel inflation and damage the global economy.
Drone and missile launches continued following the first wave of joint US-UK action on January 11.
The latest action also appears to have done little to deter Houthi action, with reports of drone activity in the region on Tuesday morning.
Mr Sunak told MPs the military action against the Houthis was just one part of a strategy which includes disrupting supplies of arms, sanctions and talks with regional powers.
Foreign Secretary Lord Cameron will head to the region “in the coming days”, Mr Sunak said.
New sanction measures will be announced soon and the Government will continue with humanitarian aid for Yemen and support a negotiated peace in the country’s civil war.
Mr Sunak spoke to US President Joe Biden on Monday night ahead of the military action and also convened a meeting of the Cobra emergency committee, including key ministers.
The wider Cabinet, Leader of the Opposition Sir Keir Starmer and Speaker Sir Lindsay Hoyle were informed at around 10pm, the time of the strikes, rather than ahead of the military action.
Sir Keir said Labour backed the “targeted action to reinforce maritime security in the Red Sea”.
He told MPs: “The Houthi attacks must stop. They are designed to destabilise us so we must stand united and strong, they bring danger to ordinary civilians who are working hard at sea, so we must protect them, and they aim to disrupt the flow of goods, food and medicines, so we must not let them go unaddressed.”
MPs will get the chance to debate the situation on Wednesday but will not be given a vote on the military action.
The Prime Minister’s official spokesman said: “It’s important that parliamentarians are able to have their say but we are acting in line with precedence.
“The powers to make a decision on this action rest with the Prime Minister.”