Police officers involved in a “serious, gratuitous and prolonged” attack on a British Muslim man that led the Metropolitan police to pay £60,000 in damages this week have been accused of dozens of previous assaults against black or Asian men.

Babar Ahmad, 34, a terrorist suspect, was punched, kicked, stamped on and strangled during his arrest by officers from one of the Met’s territorial support groups at his London home in December 2003.

After six years of denials from Scotland Yard, lawyers acting for the Metropolitan police commissioner, Sir Paul Stephenson, were forced to admit in the high court that Ahmad had been the victim of sustained and gratuitous violence during his arrest and agreed to pay £60,000 in damages.

But the Guardian can reveal that the Met was aware for years that the six officers involved were the subject of repeated complaints.

According to documents submitted to the court, four of the officers who carried out the raid on Ahmad’s home had 60 allegations of assault against them – of which at least 37 were made by black or Asian men.

One of the officers had 26 separate allegations of assault against him – 17 against black or Asian men.

The Met has confirmed that since 1992 all six officers involved in the Ahmad assault had been subject to at least 77 complaints.

When lawyers for Ahmad asked for details of these allegations it emerged that the police had “lost” several large mail sacks detailing at least 30 of the complaints.

Senior figures in Scotland Yard admit there are concerns about the conduct of the officers.

Although the Independent Police Complaints Commission supervised an investigation carried out by the Met, none of the officers has been disciplined for the assault on Ahmad and all but one are still working in the territorial support group.

Asked about the string of allegations against the officers, the Met said that all but one had been found to be unsubstantiated following inquiries.

However Fiona Murphy, the lawyer representing Ahmad, said the number of complaints should have led to a thorough inquiry.

“The horrifying nature and volume of complaints against these officers should have provoked an effective response from the Metropolitan police and the IPCC long ago,” she said.

Documents submitted to the high court and seen by the Guardian list details of some of the alleged assaults carried out by the officers:

• March 2007: one officer is accused of bundling a man into the back of a police van where he was told to “get on his knees”. When he replied this was not Guantánamo Bay he claims the officer grabbed him round the neck and “discharged his CS gas while continuing to hold his throat”. He says he was then thrown from the van, leaving him with eye, neck and head injuries. According to the document no action was taken because the complaint was either “incapable of proof” or there was “no case to answer”.

• November 2005: two of the officers were accused by a “black male” of attacking him in the back of a police van. The document states that he was subjected to “constant kicking to his head and stomach (approx 12 kicks). Head lifted off the floor by grabbing his right ear and lifting head.” The attack left the man with bruising and swelling to his face but the case was not pursued, the Met said, because of “non-cooperation” by the complainant.

• October 2005: the document stated that two of the officers were involved in another assault on a “black male”. It read: “In van repeatedly assaulted – kicks to the face, stamps on his head whilst handcuffed.” The victim said afterwards he “felt like he might die”. Vomiting and blood coming out of his ears, black swollen eye, lip busted, hands very swollen.

• June 2003: two officers accused of beating a “black male” in the back of the TSG van. “The beating continued in the van and in a search room at the station.”

The allegations against the officers came to light after the high court issued a disclosure order on 13 February demanding that the Metropolitan police release all “similar fact allegations” against the officers involved in the Ahmad case.

The Met’s legal team wrote to Ahmad’s lawyers a few weeks later to say that “because of the sheer volume of unsubstantiated complaints” against the officers they would only be able to provide a schedule of the claims rather than the files in time for the deadline.

The schedule outlining 77 separate complaints against the officers was subsequently submitted to the court, along with a sample of complaints taken from 27 files containing some of the allegations. The police said they had lost several large mail sacks detailing at least 30 other files.

During the hearing it emerged that other crucial documents, including the officers’ contemporaneous notebooks and a taped recording of an interview with the senior officer in the case, had also been mislaid.

Ahmad’s lawyers say they are now calling for a judicial inquiry into the case and seeking a criminal prosecution against the officers involved.

Murphy said: “The failure of the Metropolitan police and the IPCC to take effective action long ago against this group of officers can only be addressed by a full judicial inquiry and we will invite the director of public prosecutions to support the family’s call for an independent judicial inquiry.”

Scotland Yard said that all but one of the 77 allegations against the six TSG officers had been found to be unsubstantiated, because the complainant failed to assist them any further, the complaint was withdrawn or informally resolved, or investigated and found to be unsubstantiated.

The Met said the Directorate of Professional Standards was investigating the missing mail sacks containing 30 complaint dockets.

Sources played down the significance of the allegations against the officers, indicating that all TSG officers are often the subject of complaints because of the nature of their job as frontline officers who police public disorder as well as having an anti-terrorism role.

The Independent Police Complaints Commission has now been asked to investigate why two of the officers refused orders to give evidence in the Ahmad case at the high court.

The Metropolitan Police Authority said: “The MPA will not tolerate racism or unnecessary force and we are very concerned about the impact this case will have on community police relations in London.”

Ahmad was arrested at his home in south-west London. The court heard how officers stamped on his feet and repeatedly punched him in the head before he was forced into the Muslim prayer position when they shouted: “Where is your God now? Pray to him.”

After a sustained attack, he was forced into the back of a police van, where he was again beaten and punched before being put in a “life-threatening” neck hold and told: “You will remember this day for the rest of your life.”

At one stage, one of the officers grabbed his testicles and he was also deliberately wrenched by his handcuffs – a technique known to cause intense pain.

He has been in detention since he was rearrested in 2004 after a request from the US government over claims that he helped raise money to fund terrorist campaigns.

The court heard that no evidence had been produced against Ahmad, and that he had never been charged with any offence.

Frontline force

Created in January 1987, the territorial support group is on the frontline of policing in the capital, and its 720 officers are often the first on the scene of major disturbances.

TSG units have policed every march and demonstration in London over the past two decades, including the poll tax protests, BNP disturbances and “stop the City” demonstrations.

They also provide anti-terrorism support and have firearm and taser expertise.

They will be on the frontline again next month when they help to police protesters who are expected to gather for the G20 summit in London.