THERESA May has blood on her hands over the civil war in Yemen, Labour has suggested, as Jeremy Corbyn accused the UK Government of “colluding” in war crimes by Saudi Arabian forces.

Saudi Crown Prince, Mohammed bin Salman, has begun a three-day visit to the UK, which has so far included lunch with the Queen at Buckingham Palace and talks with the Prime Minister at No 10. Wednesday night, he was due to dine at Clarence House with Princes Charles and William.

During PMQs in the Commons, the Opposition intensified its attack on the Government’s military sales to the Gulf state as protests took place against Saudi Arabia’s involvement in Yemen and its human rights record.

Mr Corbyn took Mrs May to task, pointing out how a humanitarian disaster was happening in Yemen with millions of people facing starvation and 600,000 children suffering from cholera because of the Saudi-led bombing campaign and blockade.

Calling for a halt to UK sales as well as an immediate ceasefire on the ground in Yemen, he said: “British military advisers are directing the war. It cannot be right that her Government are colluding in what the United Nations says is evidence of war crimes.”

The PM said everyone was concerned about the appalling humanitarian situation in Yemen, pointing out how in 2017/18 the UK had increased its aid to more than £200 million.

She stressed the fact that the Crown Prince had complied with the UK’s request to open the port of Hodeidah to humanitarian and commercial supplies, “vindicates the engagement that we have with Saudi Arabia and the ability to sit down with them”.

Mrs May pointed out how the Gulf state’s involvement in Yemen had resulted from a request of the legitimate government there and was backed by the United Nations Security Council, which Britain supported.

She strongly defended the UK's "historic" ties with the Saudis, saying they had "saved the lives of potentially hundreds of people in this country"; a reference to UK-Saudi counter-terror co-operation.

Following PMQs, Mr Corbyn’s spokesman pointed to the “direct involvement” of UK military personnel in directing Saudi air-strikes in Yemen, which had led to large civilian deaths and the targeting of hospitals and schools. “There is clear evidence of war crimes in Yemen by the Saudi air force,” he declared.

Asked if Mrs May had blood on her hands, the spokesman replied: “This Government is responsible for the decisions they have taken to support this military campaign and support this aerial bombing campaign of Yemen and has directed British military personnel to take part in advising on the targeting of operations in Yemen and the consequence of that has been…very large number of civilian casualties, including very large numbers of children.”

Later, during an urgent question in the Commons, Sir Vince Cable, the Liberal Democrat leader, argued there would be "widespread concern across parties at the fact that the dictatorial head of a medieval theocratic regime is being given the red carpet equivalent of a state visit".

Labour’s Emily Thornberry accused the Tory Government of "bowing and scraping" to the Crown Prince.

As she welcomed the Crown Prince to Downing Street, the PM praised recent social reforms in Saudi Arabia, saying: "We want to work together to explore ways we can support the kingdom of Saudi Arabia to progress and intensify these reforms.

"We will also discuss how we can enhance our co-operation in tackling international challenges, including the conflict and humanitarian crisis in Yemen. I look forward to discussing here today how our relationship can continue to go from strength to strength."

The Crown Prince replied by saying that there were "huge opportunities" to boost trade between the two countries.

"I have no doubt that it's a very deep relationship and it's different; it's not only about politics or military or intelligence but also socially and economically," he added.