Theresa May has refused to say if she challenged the Saudi crown prince over allegations he ordered the killing of Jamal Khashoggi, despite vowing to have “robust” talks.

The prime minister courted controversy at the G20 summit by holding a lengthy private meeting with Mohammad bin Salman, just hours after he was confronted in public by Emmanuel Macron.

Asked, ahead of leaving Argentina, if she had asked bin Salman if he was behind what she called the “terrible murder” in the Saudi consulate in Turkey, Ms May ducked the question.

Instead, she again argued for a “full, credible and transparent investigation” by the Saudis themselves – despite the French president insisting an international probe was needed.

At the press conference, a beleaguered Ms May was also forced to fend off a suggestion that she was on one of her last trips abroad as prime minister, with MPs widely expected to vote against her Brexit deal in the Commons later this month.

Asked what her legacy was, she hit back: “There’s a lot more for me still to do – not least delivering on Brexit and being the prime minister that does take the United Kingdom out of the European Union.”

Strikingly, Ms May did not set out the other policy areas she still hopes to pursue, perhaps underlining criticism that her government is consumed by the momentous task of Brexit.

Brushing aside the resignation of universities minister Sam Gyimah, she pointed to the crucial vote on 11 December, saying: “The next nine days are a really important time for our country.”

Emmanuel Macron and Mohammed Bin Salman meet at G20 in Argentina

On Friday, Mr Macron raised the stakes over the killing of Mr Khashoggi, which the CIA believes was carried out on the personal instructions of the de-facto Saudi ruler, saying the EU would insist on international experts investigating.

Asked if she had challenged bin Salman over claims that he was directly connected with the murder, Ms May ignored the question. “It is absolutely the case that the relationship we have with Saudi Arabia means we are able to raise issues that are difficult issues for them and be clear with them on our views on things and our concerns about things," she said.

“What I said to crown prince yesterday was the importance of a full, credible and transparent investigation that identifies those who were involved and the importance of ensuring that those who were involved are brought to account.

“That is the message that we have consistently given since the terrible murder of Jamal Khashoggi and it is a message that we will continue to give.”

Earlier, Japan's prime minister appealed to Ms May to prevent a no-deal Brexit, after the two held a bilateral meeting in Buenos Aires.

The plea follows warnings from Japanese companies with operations in the UK that the extra costs and bureaucracy they would face could force them to cut their investments.

Ms May assured him that the agreement she sealed in Brussels a week ago was "a good deal for businesses in the UK, including the many Japanese companies who have made significant investment”.

Meanwhile, Donald Trump cancelled his planned news conference “out of respect for the Bush family” after the death of former president George HW Bush.

The move allowed the US president to avoid questions not only on the G20 summit but also about damaging developments in the ongoing Russia investigation.

His former personal lawyer, Michael Cohen, has pleaded guilty to lying to Congress about work he did on an aborted project to build a Trump tower in Russia.