Documents destroyed by police relating to operations at Orgreave during the miners’ strike in 1984 are believed to include a report on a notorious incident in which an officer beat a man over the head with a truncheon.

In the ITV News at 10 report on the violent scenes at Orgreave, the officer, PC Martin of Northumbria police, was seen hitting the miner, Russell Broomhead, several times with his truncheon.

Northumbria police have been widely criticised since confirming that in April last year they destroyed two boxes of documents relating to the strike and the Orgreave operation. That was just months before a general election that the Labour party, which had a longstanding pledge to hold an inquiry into what happened at Orgreave, was expected to win.

The timing led to accusations that the force had destroyed the documents to avoid scrutiny of its officers’ actions.

At the Orgreave coking plant on 18 June 1984 an estimated 8,000 miners assembled for a mass picket called by the National Union of Mineworkers, met by 4,500 police officers from forces nationwide, led by South Yorkshire police.

The violence that took place, with police charging on horseback and hitting miners with truncheons, is remembered as a landmark confrontation of the bitter 1984-85 strike. A criminal prosecution of 95 miners for riot and unlawful assembly collapsed a year later after the miners’ barristers repeatedly accused police officers of lying and malpractice.

The Orgreave Truth and Justice Campaign (OTJC) has for years called for an inquiry into the police operation and the failed prosecutions. Northumbria police previously confirmed that they held documents relevant to the policing at Orgreave, including a report by a superintendent who was the liaison officer for 92 officers sent to South Yorkshire.

In 2016 Northumbria’s then chief constable, Steve Ashman, wrote to Yvette Cooper, then the chair of the home affairs select committee, explaining that the superintendent’s report detailed an incident involving a police constable.

“This officer was believed to have been involved in striking a ‘picket’ with his truncheon,” Ashman wrote. “This incident is identified as been [sic] the subject of television news reporting … the superintendent’s report details how [the PC] was ‘reported’ for the offence of assault to the director of public prosecutions (DPP). The report further outlines that the DPP subsequently decided there would be no criminal prosecution in the case.”

Joe Diviney, a historian at the University of Sheffield who is researching a PhD on the Orgreave events, pointed out that this appeared clearly to be the PC Martin incident. Martin was identified, including in police documents, as the officer who struck Broomhead, and a report was sent to the DPP who decided, on the same day Martin was interviewed, not to bring charges.

During an interview under caution, Martin denied wrongdoing, and said of the Orgreave policing: “It’s not a case of me going off half cock. The senior officers, supers and chief supers were there and getting stuck in too – they were encouraging the lads and I think their attitude to the situation affected what we all did.”

Broomhead told the Guardian: “I would still like truth and accountability for what happened. If something is wrong, it stays wrong. I never knew in all these years that a superintendent had written a report on the incident that involved me. It’s unbelievable that the police can throw that document away, without asking me and people it affects.”

Kate Flannery, secretary of the OTJC, said: “It now seems highly likely that one of the documents destroyed by Northumbria police could relate to the PC Martin attack. Any destruction of important information relating to violent police attacks on striking miners means that crucial evidence is no longer available to an Orgreave inquiry.

“This all adds to the many concerns we have about police cover-ups and justice being denied.”

A Northumbria police spokesperson said last month that the documents had been “disposed of … in line with force policy and the Data Protection Act 2018”.

After criticism, including by the Labour MP Ian Lavery, the force has since said it is investigating its own decision-making. “We very much recognise the strength of feeling and concern within our communities at the disposal of information relating to the miners’ strike,” a spokesperson said. “We can confirm, we are carrying out an investigation into the circumstances around the disposal of the material.”

The Archives and Records Association is calling for police documents to be preserved by law. The association’s chair, Ruth MacLeod, said: “Many people have no idea that police records, which are important for accountability, can be so easily destroyed. There needs to be legislation to protect them, and prevent the kind of destruction that has happened in Northumbria.”