The police officer who was cleared on Thursday of killing Ian Tomlinson at the G20 protests has been repeatedly accused of using excessive force against members of the public, it can be reported following the end of his trial.

Details of PC Simon Harwood's disciplinary history, disclosed at pre-inquest hearings and pre-trial hearings, include allegations that he punched, throttled, kneed, threatened and unlawfully arrested people. They show he avoided likely disciplinary proceedings by the Metropolitan police over an alleged road rage incident by resigning owing to ill health. He later joined another force before moving back to the Met.

The Independent Police Complaints Commission, which investigated Tomlinson's death, said it had "grave concerns" over the failure of the Met's vetting procedures. Its inquiries established that disciplinary proceedings brought against Harwood included "unlawful arrest, abuse of authority and discreditable conduct".

Most of the complaints, contained in five lever-arch files relating to Harwood's disciplinary history, were unproven. Lawyers for Tomlinson's family first presented them before the inquest into his death last year, but the presiding judge ruled they should not be disclosed. Judge Peter Thornton QC said the complaints, the first of which was lodged two years after he joined the Met in 1995, were not relevant and risked prejudicing the inquest jurors. "Would it help the jury in deciding the core issues to know about unproven allegations?" he said. "The simple answer must be no."

The Tomlinson family lawyers argued that the files shed light on Harwood's credibility as a witness and propensity to commit violence when angry. Even if unproven, they said, the complaints suggested he knowingly evaded disciplinary hearings, and showed flaws in police vetting procedures that could have prevented him from being on duty the day Tomlinson died at the G20 summit protests three years ago. "This is a rogue officer who should have faced disciplinary charges and if he had done, the likely probability is that he would not have been in that situation on 1 April 2009," said Matthew Ryder QC, counsel for Tomlinson's family at the inquest.

Prosecutors at Harwood's trial for manslaughter sought to have the jury hear evidence about two incidents involving alleged brutality by the officer. However, Mr Justice Fulford ruled that this would, in effect, mean the jury having to "conduct three trials". He said: "I have no doubt that those matters would have such an effect on the fairness of proceedings that the court ought not to admit them." Both sets of evidence can now be reported, after the end of the court case.

A pre-inquest hearing heard that the first case involved a "road rage" incident in April 2000 in which Harwood, off duty at the time, had a minor car collision and then became involved in an argument with the man driving the other vehicle.

When senior officers investigated the case, Harwood told them the other driver was the aggressor. However, independent witnesses backed the other man, who said Harwood ran at him aggressively, knocking him over and forcing him over his car door. The witnesses said Harwood identified himself as a police officer and tried to arrest the other driver for common assault.

An officer who attended the scene later noticed how Harwood amended his notes to seek to justify the arrest, which was unlawful.

The Met settled out of court with the man and paid compensation. More than a year later the force lodged disciplinary charges against Harwood. Chief Inspector Les Jones, who investigated the case, provisionally concluded that Harwood's behaviour fell "well below that expected of a police officer". Jones made it clear Harwood could face dismissal if disciplinary charges were upheld, adding in the case file: "I believe there is clear evidence that PC Harwood became involved in a situation of road rage and then abused his position as a police officer by making an unlawful arrest. I also note he has attempted now to alter his notes."

However, weeks before the misconduct hearing was due to be heard, Harwood applied to be medically retired from the Met, citing injuries he had suffered in a motorbike accident more than three years earlier. His last day at the force was 14 September 2001. But his absence did not last long – just three days later, Harwood was taken on by the same force as a civilian employee.

Within 18 months he had successfully applied to become a uniformed officer with the neighbouring Surrey police force.

In January 2004, he was again accused of using excessive force, in a complaint lodged by a fellow officer in a raid on a flat. Two officers said they saw Harwood grab a suspect by the throat, punch him twice in the face and push him into a table, causing it to break.

The arrested suspect, referred to as BE in documents cited during legal argument before the Tomlinson inquest last year, injured another officer, named as PC Newman. But despite his own injuries, Newman was reported to have said he was so shocked at Harwood's behaviour he insisted on lodging a complaint, which prompted a disciplinary investigation.

Newman told investigators that BE shouted to Harwood: "I'll fucking have you." Harwood was said to have replied: "Go on then, I'll do you all over again." According to Newman, Harwood had acted unlawfully. According to the papers cited during the pre-inquest legal arguments, he told his seniors: "I know BE is an arsehole, but I would say he was merely defending himself."

When they asked if he wanted the complaint to be pursued, Newman replied: "Yes, I agree it needs to be sorted out. I am still quite shocked, to be honest with you."

In November 2004, Harwood applied for a transfer – this time back to the Met, rejoining the force a few months later. The incident involving BE was recorded as "unsubstantiated against PC Harwood", although Ryder said the file was "woefully silent" about how the matter was dealt with.

Once back with the London force Harwood became a member of the territorial support group (TSG), which specialises in public order policing. An IPCC commissioner, Deborah Glass, said it was "alarming" that a police officer could have avoided disciplinary proceedings by retiring, and later rejoining the force.

She said the Met would need to "account for [Harwood's] re-engagement as a constable and his deployment to one of the most critical units, the TSG, given his previous record." Harwood was the subject of a number of unproven complaints after joining the TSG, including from a member of the public who said they saw him knee a suspect in the chest in Streatham High Road, south London.

The incident, in May 2005, was one of two prosecutors also sought to raise at the manslaughter trial. At a pre-trial hearing they said an independent witness reported seeing Harwood knee a man in the kidney as he lay on the ground in handcuffs.

This case was dealt by "local resolution", as was another in which Harwood was alleged to have threatened a father and daughter, telling them he would burn down their house. The allegation was recorded as involving "assault and racial abuse".

The second case raised by prosecutors at the criminal trial came in November 2008, when Harwood allegedly twisted handcuffs placed on an AA patrolman whose vehicle he had stopped.

At the inquest, Harwood's lawyers argued all the complaints against him were unproven, except for the most recent, six months before the G20 protests, in which he unlawfully accessed the police national computer.

Harwood accepted that he searched the database to find details of a driver who had been involved in a car accident with his wife.

He conceded that a fellow officer had warned him that what he was about to do was wrong. He said: "I ignored this warning, as I was of the opinion that the person was trying to make a joke of the situation I was dealing with."

Harwood told his seniors that he wanted to find details of the other motorist after speaking to his wife on the phone about the accident. He said the conversation sent him into "red mist mode".

At a hearing before Harwood's manslaughter trial his defence barrister, Patrick Gibbs QC, successfully argued that it would be wrong to put the prior disciplinary matters before the jury.

He said: "To have been able to drag up events where they occurred, one from 2005 relating to an arrest in the street and one to a stop of a motor vehicle that appeared to be speeding in 2008, in support of what we say is a rather more serious matter falls short of a pattern."