Anti-sectarian bigotry is a malign force that must be curbed.

But a year on from the offensive behaviour at football legislation coming into force, the evidence suggests the law has resulted in the surveillance and harassment of football fans who have committed no offence.

We have consistently warned that the lack of clarity in the law risks criminalising fans for something closer to partisan enthusiasm than bigotry. But cases brought to The Herald's attention amount to a disturbing catalogue of draconian and unjust treatment of individuals. These include the detention in a young offenders' institution of a 17-year-old who was refused bail then released ahead of his hearing and a police objection to a fan seeking a taxi licence because he was the subject of an application for a Football Banning Order, although a year later no such application has been made.

Other instances of people being stopped by police while out with their families or being questioned at Glasgow Airport on their way home from holiday add to the growing belief that the legislation intended to outlaw bigotry has resulted in individuals falling under suspicion because they are football fans and not because they are guilty of inciting sectarian behaviour.

As is evident from last Saturday's game between Berwick and Rangers, when the television commentator was forced to apologise for the clearly heard sectarian chanting and the continuing display of questionable behaviour by Celtic's Green Brigade, the problem at football matches has not been eradicated. Recent court cases, however, have demonstrated the practical difficulties, even when the law has been breached, of identifying an offending individual within a group of singing fans.

These difficulties have led to a large number of cases being dropped or found not proven. This is highly unsatisfactory to all concerned. It leaves the accused feeling unjustly stigmatised and the police frustrated, while the cost in time and money should concern us all. Even successful prosecutions raise important questions about the working of this law. The three-month jail sentence imposed on a Rangers fan for sectarian abuse in Inverness was notably out of step with the general move against short jail sentences. That it was changed on appeal to 150 hours of community service suggests the tendency to over-zealousness in relation to offensive behaviour at football is not restricted to the police.

Football clubs themselves, not least the Old Firm, have been actively attempting to curb all forms of prejudice. Those efforts must continue and action must be taken against those who seek to fuel hatred. The offensive behaviour law brought in by an SNP Government has been controversial from the beginning because of the practical difficulties in applying it.

If Scottish Government ministers are serious about ending bigotry, it is essential their review of this law examines the wider question of why it appears to have given rise to unacceptable practices.

Unwarranted stopping, searching and questioning of law-abiding individuals comes uncomfortably close to a new form of institutional prejudice against all football supporters. Unless checked, it can only have a negative effect on our national sport and the relationship between the police and the public which depends on mutual respect.