A CELTIC supporters' group has called for a campaign of "harassment" in a bid to fight laws some say are leading to fans being criminalised through disproportionate measures to crack down on hate crime.

Fans Against Criminalisation (FAC), an umbrella group of mainly Celtic fans including the small shareholders group the Celtic Trust, is also to launch a petition next week to call for a parliamentary inquiry into how the police behaved when an unauthorised march by the Green Brigade group of Celtic fans in Glasgow last month led to 13 arrests.

Jeanette Findlay, trustee and former chairwoman of the Celtic Trust, represented the trust at Saturday's FAC rally and march in Glasgow and urged fans to email Scottish Parliament representatives to protest against the Offensive Behaviour at Football and Threatening Communications Act, which fans fear has led to "heavy-handed" policing.

Ms Findlay, a founding member of FAC, told a crowd of 3000 in the city's George Square about an online email template they could use and added: "Let's bombard them day in day out, let's harass them the way they harass us. Let's make their lives as difficult as they have made ours and keep doing it until they stop.

"The tide is turning for these people. What happened three weeks ago crossed the line."

A demonstration is planned for April 24 outside the Scottish Parliament, when the petition will be submitted.

Ms Findlay, a University of Glasgow economics lecturer, said the act had to be removed from the statute book and police "brought under control and to leave football fans alone".

She has appealed to fans to comply with an appeal to provide witness statements over the Green Brigade arrests so police are "held to account".

The Glasgow demonstration held by the Green Brigade in March lead to accusations that police went over the top, with some accusing the now-defunct Strathclyde Police of "harassment".

Officers formed a cordon, a practice known as "kettling", near the Chrystal Bell pub at Gallowgate at around 1pm, ahead of the 4-3 home win against Aberdeen.

Campaigners are concerned this was one of the results of the act, which gives police and prosecutors new powers to tackle sectarian songs and abuse at and around football matches, as well as threats posted on the internet or through the mail.

The act created two offences, punishable by a range of penalties up to a maximum five years in prison and an unlimited fine.

Ms Findlay added: "There is not another group in society, and I am including criminal gangs, and I am including drug dealers, who are subjected to the same level of surveillance, who are searched, scrutinised, photographed, videoed, monitored, vilified, arrested and generally subjected to the most appalling and vindictive harassment.

"And for what? Not for acts of violence, or disorder or anything like that.

"But maybe for wearing a T-shirt they don't like.

"Maybe for having a banner they don't find particularly funny, maybe singing a song that makes them uncomfortable, holding views they don't agree with, maybe singing a hymn, maybe making the sign of a cross."

There was a also a march by more than 2000 fans to Celtic Park. The fans had ignored a police warning about possible arrests. Police were "delighted" with the protesters' conduct.

FAC had earlier urged fans to be on their best behaviour and for the march to be peaceful.