A Conservative bill aimed at restricting the sex trade and discouraging prostitution has passed the Senate, leaving it one step away from becoming law despite warnings it will endanger sex workers and could ultimately be found unconstitutional.

Bill C-36, passed Tuesday, was tabled after the Supreme Court struck down Canada's prostitution laws in its Bedford ruling last December. The court found the laws violated sex workers' Charter rights to safety, and gave the government one year to put in place new laws.

(What will be Canada's new prostitution laws? Read The Globe's easy explanation)

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In turn, C-36 largely criminalizes the buying of sex, rather than the selling, but could still lead to sex workers being charged by placing restrictions on when they can discuss a transaction. Critics, as such, have warned the new bill is also unconstitutional because it will once again endanger sex workers.

Nonetheless, the bill passed its third reading vote in the Senate on Tuesday, unaltered from the version that passed the House of Commons on Oct. 6. It now only needs royal assent, a formality, to become law before the old laws expire next month.

However, sex workers warn Bill C-36 will put them in harm's way by limiting their ability to speak with, and screen, potential clients, thus exposing them to abuse – a part of the bill that many have warned is vulnerable to a Charter challenge. The bill also makes it illegal to publish an advertisement by a sex worker, restricting a method some use to safely select clients.

"I foresee that this is going to create a lot of violence," said Valerie Scott, one of three sex workers behind the Bedford case. "We won't know who we're seeing. We'll have to work alone and we'll have to remain untraceable, isolated from each other. That combination is a setup for predators pretending to be our clients."

Bill C-36 passed Tuesday after Conservative senators voted down an amendment that would have removed any criminal penalty aimed at sex workers themselves. Those penalties for discussing a sale near a school, daycare or playground remain in the bill. Bill C-36 ultimately passed "on division," meaning senators agreed that a majority supported it but that it was not unanimous. They didn't vote individually.

The bill will "significantly decrease and ultimately work towards the abolition of the demand for sexual services," Conservative Senator Denise Batters said, speaking on her party's behalf. She said the decision "responds to" the Bedford ruling, a notion Senate Liberal Mobina Jaffer disagreed with. "Consensual adult sex workers will not be safe under this bill as it currently stands," Ms. Jaffer said during Senate debate.

Ms. Scott echoed that in an interview, saying Bill C-36 will endanger sex workers even though its penalties are mostly aimed at clients.

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"What it means to me is Parliament does not take the Supreme Court of Canada's opinion seriously," Ms. Scott said, adding: "The old regime made it impossible for us to work in a safe way … this is the exact same thing, with different words."

A legal challenge could be mounted on some parts of the bill as soon as it takes effect, but it may be prudent to wait for evidence to support a case against other parts of it, said Alan Young, a professor at York University's Osgoode Hall Law School who represented Ms. Scott in the Bedford case.

"It becomes a strategic choice as to whether or not [to challenge] the obviously constitutionally flawed sections and leave the trickier ones for a later date … or whether to roll the dice and try to knock everything out on the outset," Prof. Young said. He believes "a brain dead monkey should be able to successfully challenge" some parts of the bill, while others are more nuanced.

Sex workers say they will be at risk in the interim – as evidence is gathered for any legal challenge, or as any challenge works its way through the courts.