Jeremy Corbyn accused Theresa May of offering “warm words” to Saudi Crown Prince Mohammed bin Salman over the murder of a journalist and Yemen’s civil war.
He also questioned when the UK Government would follow other countries in stopping arms sales to Saudi Arabia as he criticised the Prime Minister’s actions at the two-day G20 summit in Argentina.
Mr Corbyn told the Commons: “The Prime Minister told the media she would sit down and be robust with Crown Prince Mohammed bin Salman, the chief architect of the brutal war in Yemen which has killed 56,000 people and brought 14 million to the brink of famine.
“The Crown Prince is believed to have ordered the murder of Jamal Khashoggi.
“Rather than be robust, as she promised, we learned the Prime Minister told the dictator ‘please don’t use the weapons we are selling you in the war you’re waging’ and asked him nicely to investigate the murder he allegedly ordered.
“Leaders should not just offer warm words against human rights atrocities but back up their words with action.”
Mr Corbyn later pushed Mrs May to reveal what she said to Donald Trump given the US president’s concerns over the Brexit deal.
He said: “The Prime Minister claims under her deal we can and we will strike ambitious trade deals.
“But this morning we learnt Britain’s top civil servant in charge of these negotiations wrote to the Prime Minister admitting there is no legal guarantee to be able to end the backstop.”
Mrs May, in her reply, insisted foreign secretary Jeremy Hunt and herself had been “absolutely robust” in their response to the murder of Mr Khashoggi, adding: “The coalition intervention in the Yemen was actually requested by the legitimate government of the Yemen and has been acknowledged by the United Nations Security Council.”
She added: “I did speak to President Trump in the margins of the meeting. I was clear with him that we can indeed do a trade deal with the United States of America with the deal that is on the table with the European Union.”
Mrs May said the working group between the US and UK examining the future trade arrangements has been “making good progress”.