Boris Johnson has been challenged to do more to confront the domestic human rights record of the Egyptian president, Abdel Fatah al-Sisi, including his practice of imprisoning children charged with taking part in protests against the regime.

The president, as chair of the African Union, has been in London as star speaker at the UK’s Africa investment conference, and on Tuesday met the prime minister in Downing Street. The UK has strong commercial and security ties with Egypt, which is seen as a bulwark against Islamist terrorism. Sisi is also seen as critical to resolving the Libyan civil war.

Speaking to the press at the start of the talks, Johnson said: “It’s a great pleasure to welcome President Sisi to No 10. He gave an excellent speech yesterday at our African investment summit.”

Addressing the president, he added: “I told you when I came to see you in Cairo that it would be my privilege to welcome you here.”

A string of commercial deals between UK firms and Egypt were announced on the sidelines of the summit.

The human rights charity, Reprieve, claimed young people are among 304 held in a mass trial accused of terrorism offences relating to peaceful protests. She highlighted the case of Belal Hasnein, a teenager arrested in 2016 and subjected to torture, beatings and sleep deprivation.

Maya Foa, the director of Reprieve, said: “In principle, the UK government is opposed to capital punishment in all circumstances. Face to face with a leader who uses death sentences to silence political opposition, the prime minister must show the moral courage to oppose it in practice, too.

“Too often, western leaders have expressed vague concern about human rights abuses in Egypt, while doing nothing to prevent the enforced disappearances, torture and mass trials that characterise Sisi’s rule. Belal Hasnein’s case is a reminder of the human cost of this moral abdication.”

Last week, Mustafa Kassem, a US citizen convicted in a mass trial, died after launching a hunger strike in an Egyptian prison.

President Trump has praised the “outstanding job” being done by Sisi. Johnson, the German chancellor, Angela Merkel, and the French president, Emmanuel Macron, have all shaken Sisi’s hand and rarely mention the enforced disappearances, torture and death sentences used to suppress dissent in Egypt.

Hasnein, according to the testimony of his mother, was arrested on his way to the local square in August 2016. She said there had been no build-up of protests or demonstrations ahead of his arrest and that young people regularly congregate in the square. Nevertheless she said the atmosphere in the town could be described as tense, mainly due to fear about the presence of informers, rather than any demonstrations. After his arrest and blindfolding, he was subjected to a beating, she said.

She said in written testimony: “When he arrived at the national security building, officers suspended him from the ceiling by his hands and subjected his genitals to electric shocks. They also applied electric shocks to his head. This was so severe that he lost the ability to speak for a period of time. He was provided very little food and was never allowed to change clothes. He was kept blindfolded the entire time and was made to sleep with his hands tied behind his back.

She added: “He did not want to show me his injuries, but when I hugged him he told me: ‘Be gentle, my entire body is bruised.’”

She claimed he was held in a tiny room with poor ventilation and one other cellmate. “They are forced to defecate into a bucket in their cell, and are only allowed to use a bathroom once per day,” she said. “They sleep on the ground with only one blanket. They either lie on the blanket and sleep with nothing on top of them (it’s very cold in the cells), or they sleep directly on the floor with the blanket on top of them.”

Hasnein has been accused of joining a terrorist group called Hasm, but his mother claims he has been charged because he has friends in the Muslim Brotherhood. Egypt does not regard him as a juvenile since his trial started after he had turned 18.

The Egyptian commission for rights and freedoms claims there are 82 people at imminent risk of execution in political cases.

In 2019, 320 people were sentenced to death in 170 cases, both political and criminal. In 2019, 18 executions took place in six cases.

Sisi has long been a close ally of Gen Khalifa Haftar, the commander of eastern forces in Libya believed to be behind the closure of oil ports in the country.