Human-rights campaigners have submitted an official complaint to Fifa calling for the Asian Football Confederation president Sheikh Salman bin Ebrahim al-Khalifa to be barred from the race to succeed Sepp Blatter over his alleged involvement in a clampdown on pro-democracy protestors in 2011.

The AFC president, one of seven candidates for the Fifa presidency and considered among the frontrunners in the wake of Michel Platini’s suspension, has always denied the allegations and last week branded the claims “false, nasty lies”. His spokesman has also said the “allegations are entirely false and are categorically denied by Sheikh Salman”.

But the Bahrain Institute for Rights and Democracy (BIRD) and a US group, Americans for Democracy and Human Rights in Bahrain (ADHRB), have written to Domenico Scala, chair of the electoral committee, asking for him to be struck out of the race.

The 22-page complaint points to documents on the website of the state-run Bahrain News Agency (BNA) from April 2011 that said the Bahrain FA, of which Sheikh Salman was then head, would be investigating all footballers, staff and clubs associated with pro-democracy protests.

Four days later, an article said that a committee of inquiry had been formed to investigate athletes who took part in the protests and that it would be chaired by Sheikh Salman. A week after that, the BNA reported that the BFA had levied suspensions, fines and demotions against six clubs. When the Guardian revealed the existence of the documents, published in Arabic and sitting in the archive of the Bahrain News Agency website, a spokesman for Sheikh Salman confirmed that a committee was convened but claimed it was never formally established.

“While it was proposed that Sheikh Salman lead a fact-finding committee in relation to the events of 2011, that committee was never formally established and never conducted any business whatsoever,” said a spokesman. “For the record, and in light of the recycling of historic allegations in the media, Sheikh Salman had absolutely no involvement in the identification, investigation, prosecution or mistreatment of any individuals as has been alleged.”

Associated Press reported in 2011 that more than 150 athletes, coaches and referees were suspended after being identified as having been involved in the pro-democracy protests. Among them were six footballers who played for the national side, among them Ala’a Hubail, Mohamed Hubail and Sayed Mohamed Adnan.

The six footballers seized all alleged they were tortured after being detained, according to the letter send by BIRD and ADHRB. The complaint is addressed to Scala and also Cornel Borbely, the head of the investigatory chamber of the ethics committee, and Hans Joachim Eckert, the German judge who is head of the adjudicatory arm.

“We call on the electoral and ethics committee to disqualify the candidacy of Sheikh Salman as he fails all aspects of the integrity check required for the position,” the letter concludes. All seven candidates will be subjected to an integrity check by the electoral committee before being allowed to stand in the February election. Platini’s name is on the list despite being suspended for 90 days, and potentially a further 45, by the Fifa ethics committee.

The electoral committee has said it will not rule on his eligibility until his ban is lifted or runs out.

Following Sheikh Salman’s election as AFC president in 2013, BIRD wrote to Michael Garcia, the then head of the investigatory arm of the ethics committee, asking him to investigate the claims. Then, Garcia said it was beyond his remit.

“We know that some of Bahrain’s top footballers were harassed, defamed, arrested and mistreated during Sheikh Salman’s time at the head of Bahrain’s national football association and that they never played for the national team again,” said Nicholas McGeehan, Gulf researcher at Human Rights Watch.

“It’s difficult to see how a man who either couldn’t or wouldn’t protect his national team’s finest players from beatings can safeguard the interests of the game worldwide.”

British MPs were this week in Bahrain for talks as a new British naval base opened in the Gulf state.

The Tory MP Sir Alan Duncan said: “All of my fellow British colleagues will make sure that anyone in the UK criticising Bahrain unfairly will find us telling the truth in response. Unfortunately there is a lot of ignorance in the UK with regard to this region and we intend to stand firmly against ill-informed criticism.”

He added: “From what we have seen, Bahrain is a strong example of different sects and ethnicities living in harmony and tolerance. The recent reforms have only strengthened those values.”