The Government has been attacked for allowing £4.6bn arms sales with Saudi Arabia amid calls for the Middle Eastern kingdom to end its blockade of Yemen.

SNP Westminster leader Ian Blackford said regime must “stop killing children” as he condemned the Government for failing to suspend sell arms to Riyadh during the devastating three-year conflict in Yemen.

Theresa May’s de-facto deputy Damian Green – who stood in during Prime Minister’s Questions – said the UK had “one of the most rigorous and robust defence sales regimes in the world”.

It comes as Ms May faced pressure to raise the humanitarian crisis during a three-day trip to the Middle East, where she will hold talks with leaders in Saudi Arabia and Jordan.

Thousands of people have been killed in the conflict in Yemen, which pitches a Saudi-led coalition in favour of the internationally recognised Government against Iran-backed Houthi rebels.

Mr Blackford, the Skye, Ross and Lochaber MP, said: “The UK Government has received £4.6bn in selling arms to Saudi Arabia, since the war in Yemen began.

“A war which has created a devastating humanitarian crisis. Yemen is now on the brink of famine and Unicef has said 150,000 children will die by the end of this year.

“Don’t you agree that the best thing the Prime Minister can do with her meetings today is follow the example of the Netherlands and suspend licences for arms sales to Saudi Arabia and stop killing children?”

Mr Green hit back, saying: “You said the Government will receive the money – it will be the companies that receive the money and therefore their workers.

“He can take that position if he wants , I know it’s the Labour Party’s position as well, but that would certainly entail significant job losses.

“Now what is very important not only that we have the robust regime which I talked about but that absolutely we continue the humanitarian efforts that we make to try and alleviate the terrible conditions in Yemen.”

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The UK is the fourth largest humanitarian donor to Yemen and continues to support Saudi involvement in the conflict, which is backed by the UN Security Council, he said.

The Prime Minister was expected to raise the threat of famine in Yemen when she meets Crown Prince Mohammed bin Salman of Saudi Arabia on Wednesday.

Efforts to curb the humanitarian crisis have been hampered by the Saudi-led coalition's blockade of ports, which has been partially eased to allow UN aid ships to bring food supplies.

Mark Goldring, Oxfam chief executive, said: "In the midst of the world’s worst cholera epidemic on record and with the country on the brink of the worst famine in recent years, the UK needs to do more than talk tough - it needs to exert real pressure and take action.

"As the country responsible for drafting UN Security Council resolutions on Yemen, the UK should be ready to step up international pressure on Saudi Arabia to persuade them to lift the blockade and on all sides push for peace.

"The Government should stop authorizing arms sales which are fuelling the war in Yemen. It is a shameful contradiction that the UK is allowing for profiting out of people’s suffering.