The brother of a leading Saudi women’s rights campaigner who is allegedly being tortured and sexually harassed in prison is fearful her treatment could be worsening.

Loujain al-Hathloul, who defied the kingdom’s recently overturned ban on female drivers, was arrested in May 2018 along with 10 other women’s rights activists in Saudi Arabia.

The 29-year-old campaigner’s family and Human Rights Watch have alleged in recent months that she and other female detainees have been tortured and sexually harassed in jail.

Ms al-Hathloul has told her parents she has been held in solitary confinement, beaten, waterboarded, given electric shocks, sexually harassed and threatened with rape and murder.

Walid al-Hathloul, her 31-year-old brother, said the family had tried to contact a number of government bodies about his sister’s detainment but they had been given no clear information.

“I am worried about her because we are not getting any official response. It is possible that it could be getting worse,” he said. “The lack of transparency has raised many red flags about justice and the rule of law.”

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He said the family did not know where the activist, who was ranked third in 2015’s list of most powerful Arab women in the world, was for a month after she was initially arrested last May.

Mr al-Hathloul, who lives in Ontario in Canada, said at first he thought she would simply be questioned and then released, and he initially remained totally oblivious to allegations of mistreatment.

“We never thought there would be brutal treatment and torture,” he said. “We did not know all this madness until November of last year and then she started to share everything with my parents. They saw that her hands were shaking, they saw the signs of torture – the burns and bruises on her legs.”

He said his sister says she has been whipped, beaten, electrocuted in a chair and harassed on a frequent basis – with masked men sometimes waking her up in the middle of the night to shout threats.

She has also told her family she has been forced to endure “verbal sexual abuse” and “sexual harassment” at the hands of her torturers.

“One of the interrogators put his legs on my sister’s legs like you would put your legs on the table. He was smoking and puffing in front of her face,” said Mr al-Hathloul.

His comments come after the European parliament on Thursday urged Saudi Arabia to release women’s rights campaigners from prisons.

They also called for the country to abolish its male guardianship system, under which women have to seek permission from their guardian on issues such as getting married.

Saud al-Qahtani, a former top adviser of Crown Prince Mohammed bin Salman, is alleged to have been present during at least one of Ms al-Hathloul’s interrogation sessions.

“Qahtani was supervising the torture. He said, ‘We will rape you, we will kill you, we will cut you in pieces and put you in the sewage system’ to her sometime last summer,” her brother said.

Saudi prosecutors allege Mr al-Qahtani played a major role in the events that led to Jamal Khashoggi’s killing in the kingdom’s Istanbul consulate last October.

The former royal court communications chief, a powerful adviser, was removed from his post after Riyadh pinned the blame for the murder of the Washington Post columnist on him and other high-ranking officials.

“Qahtani was said to be dismissed because of Khashoggi but it doesn’t seem that he was really dismissed. He was dismissed officially but it looks like he is still running the media and the trolls on Twitter,” Mr al-Hathloul said.

He said his sister submitted a complaint about her “torture and conditions” when she was in Dhahban prison, a maximum security jail near Jeddah, but the complaint did not go through. Mr al-Hathloul said she had submitted another complaint in al-Ha’ir prison, near the capital of Riyadh, where she is currently being held.

Mr al-Hathloul said the complaint was filed early this month but the administration has yet to issue a reference number which it needs in order to process the grievance. He said a delegation from the governmental body Saudi Human Rights Commission had gone to visit her after reports were published about her torture.

Mr al-Hathloul said: “They asked her to write her testimony about the torture. When she finished writing it, she asked the three people, ‘Will you protect me?’ They said they could not. She ripped up the paper and cried because she felt it was useless.”

He explained he could not return to Saudi Arabia because he and his family had been banned from travelling outside of the country – adding there was “no legal basis” for the ban. “I would love to go back and contribute to the country but why would I go back to Saudi Arabia if I can’t leave?” he said.

His sister, who appeared alongside the Duchess of Sussex, Meghan Markle, at the One Young World summit in Ottawa in 2016 for young leaders, peacefully campaigned alongside other activists for years to allow women the right to drive.

The University of British Columbia graduate has been arrested and released several times for defying the driving ban. In 2014 she was detained when she attempted to drive across the border from the United Arab Emirates.

Ms al-Hathloul served 73 days at a juvenile detention centre as a result and documented many of her experiences on Twitter. She was one of the first women to run for a seat on a municipal council in 2015 but lost.

The official Saudi Press Agency has said the women’s rights defenders were accused of “suspicious contact with foreign entities”.

Riyadh has previously denied allegations of torture after the publication of an initial Human Rights Watch report alleging the abuse in November.

“The kingdom of Saudi Arabia’s judiciary system does not condone, promote or allow the use of torture,” a Saudi official said. “Anyone, whether male or female, being investigated is going through the standard judiciary process led by the public prosecution while being held for questioning, which does not in any way rely on torture either physical, sexual or psychological.”

On a visit to Washington DC earlier this month, Saudi foreign minister Adel al-Jubeir said Saudi authorities were looking into allegations of mistreatment.

He defended the women’s imprisonment and accused them of being a threat to national security.

“When Loujain was arrested we preferred not to appear on media because we thought that being silent would solve the problem. It actually made it worse,” her brother said.