Theresa May has announced a plan to send British military trainers to Jordan to boost the nation's air force at the start of a three-day tour of the Middle East.

The programme’s aim is to help the country fight Isis but comes amid controversy surrounding the Saudi-led military campaign in Yemen, which also involves Jordan.

The Prime Minister wants to focus her visit, taking in both Jordan and Saudi Arabia, on tackling the Jihadi group and deepening trade ties.

But the trip was accompanied by an embarrassing announcement from the Metropolitan Police that its war crimes unit is considering an investigation into Saudi activities in Yemen.

Ms May said: “It is clearly in the UK's security and prosperity interests to support Jordan and Saudi Arabia in tackling regional challenges to create a more stable region, and in delivering their ambitious reform programmes to ensure their own stability.

“An even deeper partnership with these countries, and greater knowledge and understanding of one another, will increase our ability to address the issues that concern us, including the promotion of international standards and norms.

“To tackle the threats we face from terrorism and from geopolitical instability, we must meet them at their source.”

The child victims of Yemen’s civil war

She added: “Jordan is on the front line of multiple regional crises and I'm clear that by working with them, we are helping keep British people safe. Likewise in Saudi Arabia, we must never forget that intelligence we have received in the past from that country has saved potentially hundreds of lives in the UK.”

On Tuesday Ms May will head to Saudi, the UK's largest trading partner in the Middle East with goods and services exports totalling £6.6bn in 2015. Talks are set to focus on stronger ties following the vote for Brexit.

The Prime Minister has faced repeated calls to suspend arms sales to Riyadh amid claims of widespread human rights abuses in Yemen during the coalition bombing campaign it is leading, which includes Jordan.

The Saudis back the war-torn country's internationally recognised government against Iran-backed Houthi rebels.

2.1 million children are facing famine in Yemen

Britain has continued to allow arms sales, with more than £3.3bn of exports since the bombing began in March 2015. At least 10,000 people have been killed during the war, according to the United Nations.

Foreign Secretary Boris Johnson apologised at the weekend to the Saudi government after an activist in London tried to carry out a citizen's arrest of one of the Gulf state’s generals, while another protester threw an egg at the senior officer as he arrived at an event.

But further embarrassment has been caused after the Met made its announcement, in a statement: “On Thursday 30 March 2017, the Metropolitan Police Service received a referral of an allegation of war crimes, made against Saudi Arabia, committed in Yemen.

“Following receipt of the referral, the MPS war crimes team began a scoping exercise and contacted those making the allegations.

The situation in Yemen Show all 14 1 /14 The situation in Yemen The situation in Yemen Houthi supporters trample on a US flag during a gathering mobilizing more fighters into several Yemeni battlefronts, in Sana'a, Yemen EPA The situation in Yemen People carry the coffins of men, who were killed in the recent Saudi-led airstrikes during their funeral, in the Old City of Sanaa, Yemen AP The situation in Yemen Pro-government fighters give food to Yemeni children on the road leading to the southwestern port city of Mokha. Yemeni rebels are putting up fierce resistance in a key Red Sea port city where they are encircled by pro-government force Getty Images The situation in Yemen A Yemeni stands in front of a graffiti protesting US military operations in war-affected Yemen, in Sana'a, Yemen. According to reports, US Special Forces troops allegedly disembarked from US helicopters in the Yemeni town of Yakla and attacked several houses belonging to members of the terrorist group Al-Qaeda, killing three high-ranking Al-Qaeda members and nine civilians, six women and three children. One American serviceman has been killed and three injured in the attack EPA The situation in Yemen US Special Forces troops allegedly disembarked from US helicopters in the Yemeni town of Yakla and attacked several houses belonging to members of the terrorist group Al-Qaeda, killing three high-ranking Al-Qaeda members and nine civilians, six women and three children. One American serviceman has been killed and three injured in the attack EPA The situation in Yemen A Yemeni female fighter supporting the Shiite Huthi rebels, and carrying weapons used for ceremonial purposes, takes part in an anti-Saudi rally in the capital Sanaa Getty Images The situation in Yemen Yemeni female fighters supporting the Shiite Huthi rebels, and carrying weapons used for ceremonial purposes, take part in an anti-Saudi rally in the capital Sanaa Getty Images The situation in Yemen A boy shouts slogans next to pro-Houthi fighters, who have been injured during recent fighting, during a rally held to honour those injured or maimed while fighting in Houthi ranks in Sanaa, Yemen Reuters The situation in Yemen Balls of fire and smoke rise from a Houthi-held military camp following alleged Saudi-led airstrikes, in Sana'a, Yemen EPA The situation in Yemen Yemenis search under the rubble of damaged houses following reported Saudi-led coalition air strikes on the outskirts of the Yemeni capital Sanaa Getty Images The situation in Yemen A Yemeni boy looks on as Yemenis search under the rubble of damaged houses following reported Saudi-led coalition air strikes on the outskirts of the Yemeni capital Sanaa Getty The situation in Yemen A Yemeni boy sits amidst the rubble of damaged houses following reported Saudi-led coalition air strikes on the outskirts of the Yemeni capital Sanaa AFP/Getty The situation in Yemen Marine One with US President Donald Trump flies with a decoy and support helicopters to Dover Air Force Base in Dover, Delaware, for the dignified transfer of Navy Seal Chief Petty Officer William 'Ryan' Owens who was killed in Yemen Getty Images The situation in Yemen US President Donald Trump aboard the Marine One to greet the remains of a US military commando killed during a raid on the al Qaeda militant group in southern Yemen on Sunday, at Dover Air Force Base, Delaware, US Reuters

“There is no investigation at this time, and the scoping exercise continues.”

The Saudi visit comes days after the Government was pressed to explain why the state “consistently features in the back story of terrorists”, including the Westminster attacker.

Khalid Masood, the extremist who carried out the 82-second rampage on 22 March, worked in the country for several years.