CONCERNS have been raised over the handling of a complaint to prosecutors into claims inaccurate evidence by a police sergeant led to the conviction of two football fans.

A leading lawyer and campaigners have accused the Crown Office of failing to properly act on the allegations against the officer, whose evidence has previously been questioned by sheriffs.

The move follows the separate decision by the Crown Office to formally raise concerns with Police Scotland's internal watchdog over the quality of evidence given in a case where a football fan was acquitted following a notorious 'kettling' incident.

It also comes as new official statistics shows a steep rise in the number of successful prosecutions under the controversial Offensive Behaviour At Football Act.

In the latest complaint, the Crown Office, Lord Advocate and Police Scotland have said they will not be taking forward a complaint of perjury against a sergeant within Police Scotland's specialist football unit, the key witness in a high-profile Offensive Behaviour case.

Reasons cited for not proceeding with the complaint include insufficient evidence to establish the precise terms of the officer's testimony, issues around the material impact on the outcome of the case and whether the evidence was knowingly false.

But lawyers for William Donnelly and Martin Walsh, who were convicted under the Offensive Behaviour Act, have accused the Crown Office of inconsistency in how it investigates such complaints.

Paul Kavanagh, who has acted in a high number of football cases, said: "In the previous (kettling) case I gave a statement for three hours to the police. I have had no contact from anyone in relation to this case.

"What is being contested by the complainers was said in open court and the evidence by the officer was very specific. The complainers have been able to produce evidence from numerous supporters' groups which is at odds with the police evidence.

"If perjury has been committed that's for someone else to decide but I've never been asked to assist in any investigation into the Walsh and Donnelly complaints and neither has the accused."

Walsh and Donnelly, both from Dumbarton, were charged with engaging in behaviour which was likely to incite public disorder by singing the "Roll of Honour", which commemorates the 1981 hunger strikes involving the Provisional IRA and INLA.

Both claim they did not know the song was illegal, based on previous acquittals. The two were given six-month football banning orders.

Campaign group Fans Against Criminalisation (FAC) has claimed the evidence given by police in the initial conviction and cited in the refusal of their appeal was grounds for an investigation.

Specifically it has questioned the officer's claim that Celtic and various supporters' clubs had warned fans of the undesirability and dangers in singing this particular song and the pair would have been aware it was banned as a result.

But Celtic Football Club has disputed it ever publicly indicated the song was sectarian or otherwise, as have all major supporters' groups.

FAC's Jeanette Findlay said: "I reported a serious crime in March and it took until October before anyone took a statement from me or looked at the evidence I had. I have been stonewalled at every turn since."

A Crown Office spokesman said: “Following careful consideration of all the facts and circumstances, including the opinion of the appeal court in upholding the convictions of Walsh and Donnelly, the Crown decided that there was insufficient evidence to prove that a criminal offence had been committed by any witness.”

A Police Scotland spokeswoman said: "This matter was investigated by Police Scotland and reported to the Criminal Allegations Against the Police Division, Crown Office and Procurator Fiscal Service."

Meanwhile, new figures show a conviction rate of 82 per cent in Offensive Behaviour cases where proceedings have concluded in the last year, up from 57 per cent the previous year.

But with only 76 people charged, the report on the statistics said: "It is important to bear in mind that the number of people proceeded against for these offences is low and the conviction rate varies considerably from year to year."