TORONTO - A protester who was among the hundreds of people detained during the G20 summit is spearheading a $45-million class-action lawsuit that claims police acted unlawfully and violated constitutional rights.

Sherry Good, a 51-year-old office administrator, said Friday she was corralled by cops for four hours on June 27 -- a day after a group of violent, black-clad protesters rampaged through the downtown core.

Police in riot gear, using a tactic called kettling, encircled a peaceful crowd of protesters on trendy Queen Street West and refused to allow those caught inside to leave.

The group, which included journalists, had no water, no food, no toilets and no idea what was happening, said Good.

She used one word to describe the experience: "Terrified. That's about the only word I can use ... terrified."

Good wasn't arrested, but said she couldn't sleep that night and suffered a panic attack the next day.

"But the biggest consequence of that weekend is that I have lost my trust in the police," she said from the front lawn of the Ontario legislature.

"Now I am nervous when I see a police car. I consistently look over my shoulder. Sadly, it will take a long time to regain that trust."

Good, who was approached by a group of lawyers after she told her story on a website, said she's launching the class action on behalf of more than 800 others who were held without charge.

More than 1,000 people were detained by police that weekend after protesters using so-called Black Bloc tactics broke away from a peaceful rally and ran through the city's downtown core, smashing windows and burning police cruisers.

The vast majority of those detained were released without charge within 24 hours. Some spent the night in a film studio that was converted into a temporary detention centre.

A judicial inquiry is what's really needed, but the lawsuit is a start, said Murray Klippenstein, one of the lawyers behind the class action.

Canadians are proud of the freedoms they have, but that sense of privilege suffers when they see the arrest and imprisonment of hundreds of people who didn't appear to be breaking any laws, he said.

"In fact, they were just exercising their basic rights that millions of us thought we had -- the right to speak up," Klippenstein said.

The class action, filed Thursday in the Ontario Superior Court of Justice, names the Toronto Police Services Board and the Attorney General of Canada.

It argues that the vast majority of arrests and detentions over the course of the G20 weekend were unlawful, unjustified and unconstitutional.

None of the allegations have been proven in court.

If approved by the court, the lawsuit would cover anyone who was arrested or detained by police June 26-27 and later released without charge. It also seeks findings and remedies for the conditions at the detention centre.

Lawyers involved in the suit said similar lawsuits in Washington and Seattle have been approved as class actions by the courts.

"As a result, we believe there is clear legal precedent that will assist our courts in reaching a determination that we hope will ensure this claim is able to be advanced as a class action," said lawyer Eric Gillespie.

The Ontario government wasn't named in the suit, but critics say there are still plenty of unanswered questions about its conduct before and after the G20.

Premier Dalton McGuinty came under heavy fire for the widespread confusion about the extent of police powers during the G20.

The governing Liberals secretly passed a law in early June giving police the power to stop, search and detain anyone trying to enter the G20 security zone.

But many believed the regulation allowed police to arrest people who came within five metres of the summit security fence if they didn't produce identification -- a mistake that wasn't cleared up until the G20 was over.

McGuinty not only misled his own parliament about the effect of that regulation, but also the public and the police, said NDP justice critic Peter Kormos.

"That's outrageous behaviour for a premier," he said. "And the fact that that remains unexplained cries out for a full public inquiry so that there can be an investigation into that regulation, the process, who asked for it, why they got it."

Ontario's ombudsman is investigating the so-called fence law after receiving dozens of complaints, and is expected to deliver a report in October.

McGuinty has refused to apologize for passing the law and has dismissed calls for a public inquiry.

Klippenstein said the fence law had little to do with the events described in the class action, although other parties may be named later, such as the Ontario Provincial Police.

The Toronto Police Services Board is planning to conduct a review of the G20 summit, but some are skeptical about how far it will be able to go in getting answers from bodies that don't fall under its jurisdiction. Board chairman Alok Mukherjee declined to comment on the lawsuit Friday.

Ontario's independent police watchdog is also investigating public complaints about police actions during the G20.

Criminal cases against a core group alleged to have been behind the violence on June 26 continues to wind their way through the courts.

On Friday, police released another batch of photographs of suspects wanted for alleged crimes committed during the G20.