A group of British MPs and lawyers is calling for access to women’s rights activists detained in Saudi Arabia, following allegations that they have been subjected to torture and sexual assault in prison.

More than a dozen were imprisoned in a crackdown by authorities in May last year, just ahead of the country’s ban on women driving being lifted. Many of them were prominent in the campaign to remove the ban.

Some were later released without charge, but at least eight women and a number of male supporters of the movement remain in custody. Human rights groups have said at least three of the women have suffered torture and sexual assault in Dhahban Prison, where they are being held, and all have been denied access to lawyers.

A cross-party panel of British MPs released an open letter on Wednesday addressed to the Saudi ambassador to the UK, Prince Mohammed bin Nawwaf bin Abdulaziz, requesting permission to visit the detained activists to check on their condition.

“There are credible concerns that the conditions in which the Saudi women activists are being detained may have fallen significantly short of both international and Saudi Arabia’s own standards,” wrote Conservative MP Crispin Blunt, who chairs the panel.

“No person should be subjected to the type of treatment that has allegedly been inflicted upon these women activists while in detention. The implications of activists being detained and tortured for exercising their freedom of speech and conducting peaceful campaigns is concerning for all individuals seeking to exercise their human rights in Saudi Arabia,” he wrote in an open letter.

Mr Blunt, chair of the All-Party Parliamentary Group for Saudi Arabia, is joined on the panel by Liberal Democrat MP Layla Moran, and Dr Paul Williams from Labour.

The crackdown on women activists came just weeks ahead of the removal of the driving ban on 24 June, seen as a step forward for equality in Saudi Arabia. The arrests were widely interpreted as a message to campaigners that changes in the country would be delivered from the top, and to discourage similar campaigns on other issues.

Saudi Women celebrate their freedom to drive Show all 8 1 /8 Saudi Women celebrate their freedom to drive Saudi Women celebrate their freedom to drive A Saudi woman gestures while driving in Dhahran, Saudi Arabia Reuters Saudi Women celebrate their freedom to drive A Saudi woman drives at night in Al Khobar, Saudi Arabia Reuters Saudi Women celebrate their freedom to drive Saudi women embrace as they celebrate the lift of the female driving ban in Saudi Arabia Reuters Saudi Women celebrate their freedom to drive A Saudi woman straps in Reuters Saudi Women celebrate their freedom to drive A Saudi woman drives to work in Jeddah, Saudi Arabia Reuters Saudi Women celebrate their freedom to drive Fadya Fahad is one of the first female drivers for Careem, a ride sharing company in Saudi Arabia Getty Saudi Women celebrate their freedom to drive A Saudi woman stops at a petrol station while driving to work in Jeddah, Saudi Arabia Reuters Saudi Women celebrate their freedom to drive A Saudi woman waits for coffee on the commute in Jeddah, Saudi Arabia Reuters

Among those detained were Loujain al-Hathloul, Aziza al-Yousef, Eman al-Nafjan, Nouf Abdelaziz, Mayaa al-Zahrani, Samar Badawi, Nassima al-Saada, and Hatoon al-Fassi, all women’s rights activists. Ibrahim al-Modaimeegh, a lawyer; Abdulaziz Meshaal, a philanthropist, and Mohammed Rabea, a social activist, were also detained because of their outspoken support for women’s equality.

Some of the detained have been charged with “suspicious contact with foreign parties”, and state media has labelled them “traitors”.

Since being detained without charge in May last year, a number of the activists have been “repeatedly tortured by electrocution and flogging, leaving some unable to walk or stand properly,” according to a report by Amnesty International in November last year.

Support free-thinking journalism and attend Independent events

“In one reported instance, one of the activists was made to hang from the ceiling, and according to another testimony, one of the detained women was reportedly subjected to sexual harassment, by interrogators wearing face masks,” the report added.

A Human Rights Watch report said: “At least three women were subjected to sexual harassment and assault, including forced hugging and kissing and exposure to sexually suggestive gestures.”

In December, the UN Committee against Torture called on Saudi Arabia to free the activists, citing allegations of “torture, sexual harassment and other forms of ill-treatment during interrogation”.

Saudi Arabia has denied the allegations of torture, saying: “These recent reports by Amnesty International and Human Rights Watch are baseless.”

It added that they were “simply wrong”.

Mr Blunt wrote in the letter that the panel had requested a prison visit “to review the conditions under which they are being held along with permission to carry out an independent medical evaluation of their current health”.