MONTREAL - It wasn't so long ago that prostitutes were a common sight on Montreal's historic lower Main, standing on street corners in high-heeled boots.

For years, the intersection of Ste. Catherine Street and St. Laurent Boulevard was the epicentre of the city's bustling red light district.

Over the past decade, though, nearly all the strip clubs and street-level prostitution has been pushed to the outskirts to make way for a city-backed development of office buildings and trendy shops.

The changes may be good for business -- but they also have sex workers worried about their own safety.

Repression from police has pushed prostitution into more dangerous, isolated parts of the city, making sex workers more vulnerable to violence, said Anna-Louise Crago a sex worker and a clinical co-ordinator at a sex-trade support and advocacy group known as Stella.

"There's incredibly heavy police repression against any sex workers trying to work on the street in this area," said Crago.

"Criminalization and police repression against sex workers, our clients, and our work places make it impossible to work in safer conditions."

Experts say the same pattern of repression has been repeated in other cities across Canada, making prostitution a more dangerous job.

In Vancouver, police engaged in a decades-long campaign to move prostitutes into the more isolated Downtown Eastside, where serial killer Robert Pickton spent years hunting his victims, said John Lowman, a criminologist at Simon Fraser University.

That made it easy for Pickton and other predators to target women, said Lowman, who testified at the Pickton inquiry.

"One of the things that just about everybody agrees on is that the current laws don't make sense," he said in an interview. "It's a problem that needs a fundamental solution."

It's not illegal to be a prostitute in Canada, but many of the activities associated with prostitution are classified as criminal offences.

Lowman said the ambivalence has caused confusion in the courts and made it difficult for police to do their job.

Efforts to protect sex workers often appear to be at odds with the police's attempt to crack down on prostitution.

That seemed to be the case in December when Ottawa police chief Vern White, faced with a possible serial killer targeting prostitutes, warned them to be extra cautious.

Advocacy groups countered that it was the force's very own tactics of aggressive policing and repression that had forced them into more dangerous situations.

A study by the B.C. Centre for Excellence in HIV/AIDS suggests that's the case.

The report, based on interviews with more than 200 sex workers between 2006 and 2008, found a link between prostitutes who reported having been harassed or assaulted by a police officer and the likelihood they were victims of violence in future.

In Montreal, Stella has recorded between 50 and 60 cases of violence, including rape, brutal beatings, and attempted murder against sex workers annually.

Yet only four or five cases reach the courts every year. The victims are often afraid to press charges, said Emilie Laliberte, director of Stella.

Across the country, 171 female prostitutes were murdered between 1991 and 2004, and that 45 per cent of those cases went unsolved, a 2006 Statistics Canada report found.

But because many such killings go unreported, that number is "almost certainly lower than the real figures," a House of Commons sub-committee concluded in 2006.

Since then, of course, grim details have emerged about Robert Pickton, who murdered sex workers in the late 1990s and early 2000s in the Vancouver area.

The debate about how to cut back on the violence may end up being settled by the courts.

The federal and Ontario governments are trying to overturn a lower court ruling in which a judge struck down three laws against prostitution, saying they force people in the sex trade to choose between obeying the law and keeping themselves safe.

Sex workers argue that the laws prevent them from working indoors where it's safer, taking time to talk to a potential client to assess the risk they pose and hiring bodyguards.

The Harper government maintains that protecting victims of exploitation and supporting the enforcement of existing laws should be a priority.

Whatever the Appeal Court decides, its likely the ruling will be appealed to the Supreme Court of Canada.

The top court's ruling in support of the Vancouver safe-injection site Insite has given advocates cause for optimism. They are hopeful the Harper government will be forced to make changes to the country's prostitution laws.

"That judgment gives us a lot of hope," said Laliberte, who is also a former sex worker.

"For us, it's a really important sign that even though the government doesn't want to respect our rights the courts will."