Formula One has been accused of “looking the other way” by human rights groups in the case of an activist who was beaten, sexually abused and jailed for protesting against the Bahrain Grand Prix.

Najah Yusuf, who was imprisoned after a series of Facebook posts in April 2017 that were critical of the race and the regime, has not been allowed to see her family for six months. Initially, as the Guardian revealed in November, Formula One admitted to having “concerns” about Yusuf’s case. However, in a letter to Human Rights Watch and the Bahraini Institute of Rights and Democracy (Bird) on Monday, it said it had been assured Ms Yusuf’s conviction “had nothing to do with peaceful protest around the Bahrain grand prix”.

In a letter seen by the Guardian, it added the Bahrain government had also promised: “Anyone who merely criticised or continues to criticise Formula 1 in Bahrain is free to do so.”

F1’s willingness to accept the word of the Bahraini regime has infuriated human rights groups, who point out the court judgment against Yusuf said she had written “no to Formula races on occupied Bahraini land” in one post, while in another she claimed F1 coming to her country was “nothing more than a way for the [ruling] al-Khalifa family to whitewash their criminal record and gross human-rights violations”.

She also called for a “Freedom for the Formula Detainees” march to put the spotlight on protestors who had been jailed for criticising the race, which was cancelled in 2011 after demonstrations in the country.

Aya Majzoub of Human Rights Watch said F1 was guilty of “looking the other way” and was “complicit in Bahrain’s attempted use of the grand prix to whitewash those abuses”. He added: “Taking the Bahraini government’s assurances that no punitive measures will be directed against activists for peacefully opposing the grand prix is absurd given Bahrain’s track record of repressive measures to close down protests opposing the races in the country.”

Human rights groups also claim the Bahrain regime has a record of trying to punish its critics, most notably the footballer Hakeem al-Araibi, who fled to Australia in 2014 but was detained on his honeymoon in Thailand in November at the request of Bahraini authorities and held for almost three months.

Sayed Ahmed Alwadaei, the director of advocacy at Bird, said he was stunned at F1’s response and said it was sending the world an “appalling message that its supposed commitment to human rights in reality means nothing” just weeks before the 2019 Bahrain grand prix.

Meanwhile the Liberal Democrat peer Lord Scriven told the Guardian he would be pressing Yousif’s case with senior F1 figures next week. He added: “It is clear the senior people running F1 are not taking their responsibilities seriously in dealing with human rights abuses that are a direct result of the Bahrain grand prix. The case of Najah exemplifies this. F1 are happy to be a fig leaf for the Bahraini authorities who use the grand prix to portray a picture to the world that hides the systematic human rights abuses of those who wish to stand up and have true freedom of expression.

“If F1 leaders won’t deal with human rights abuses that are directly linked to their sporting events, then maybe it’s time to take the case direct to the sponsors, teams and individual drivers.”

The Bahrain regime insists it has a “zero-tolerance” towards mistreatment of any kind. In a statement it said: “Najah Yusuf’s conviction does not relate to Bahrain’s grand prix. Any suggestion that she was convicted of a related offence is categorically incorrect. She was charged and subsequently convicted by a court of terror offences. Furthermore, Najah Yusuf’s defence did not claim during her trial that her right to free speech had been infringed. Peaceful protests of any kind are protected by Bahrain’s constitution and do not constitute a crime.”