The government is reworking Canada's prostitution laws, but some critics say the bill is missing a key piece: a definition of sexual services.

The House justice committee heard from 60 witnesses over more than 20 hours of meetings this week, and fielded a range of criticism of the bill — along with praise from a number of organizations for criminalizing the purchasers who create the demand for paid sex.

But one seemingly big gap is the lack of an explanation for what services go along with the activities that would be crimes if C-36 becomes law.

The Supreme Court struck down Canada's existing laws around prostitution last December, ruling many of them breached sex workers' rights to security and freedom of expression, and gave the federal government a year to craft new laws that respect the Charter of Rights and Freedoms.

"I think it's both a key thing and an example of a bigger problem with the bill," Elin Sigurdson, a lawyer with Vancouver's Pivot Legal Society who participated in the Supreme Court case, told CBC News.

"When the thing that's being regulated — it's described as sexual services, [but] the bill doesn't contain a definition of what it is. That's a real vagueness problem."

Sigurdson said there's a legal principle that says laws have to be knowable — they can't be arbitrarily applied and should be articulated. She added that other parts of the bill, like sections referring to legitimate relationships and where children may reasonably be expected to be present, are equally vague.

On this matter, it seems Pivot agrees with the association representing exotic dance clubs.

'Not the Bill Clinton definition'

Tim Lambrinos, who represents the Adult Entertainment Association of Canada, told MPs on the committee Wednesday that sexual activity needs to be defined in the bill. His concern is that massage parlours cut into the strip club business and put pressure on dancers to perform sexual services.

Lambrinos referred to a definition created by a lawyer and listed a number of explicit acts.

"It's not the Bill Clinton definition of sex," he said.

Dominatrix Terri-Jean Bedford, aka Madame de Sade, right, sits next to personal slave Suzy and other guests in a bondage hotel and bed and breakfast in Toronto. Just what qualifies as sexual services isn't defined in C-36, the government's new prostitution bill. (Kevin Frayer/Canadian Press)

"There's a long list of very poignant, detailed things, and it defines sexual activity."

Conservative MP Joy Smith, an advocate for the bill who's sat on the committee this week, said there's no need to define sexual services.

"Everybody pretty well knows what it's about. What needs to happen is talking about stopping the predatory nature of prostitution and human trafficking. Stopping the brutalization of the women and children and young boys involved, and that is the focus of the bill," she said.

"I mean, everybody can go into the minutiae of is this sex, is this not sex. Generally speaking, the world knows what sex really is.... What we're looking at is whatever the women are doing. It's the brutalization of them."

'Bizarre' discussion for Parliament

Despite a week that saw MPs questioning current sex workers and probing how prostitution works, the idea of debating what makes a sex act still seems dissonant.

Sigurdson agrees. "It is a bizarre thing to talk about in Parliament," she said. But she raised questions about the current lack of clarity. Would a lap dance be included as a sexual service? Or a sexual performance viewed via web cam?

"Because there's a purchaser, there's a performer, there could arguably be the purchase of a sexual service. But there's not been any touching. So I don't know," Sigurdson said.

Lambrinos noted many massage parlours advertise using acronyms rather than listing specific acts and said they create "a negative impact on our performers."

"Because they realize you can go over there, our customers, and get more bang for your buck. But meanwhile a lap dance is not intercourse, and then there is pressure put on. So they've been a nuisance to our industry."

Lambrinos said the intentions behind C-36 may be good, but "you don't even define what sexual activity is, and there's no tools in place for the [police] to implement."

A spokeswoman for the department of justice said it's ultimately up to the courts to decide.

"Whether a particular act constitutes a sexual service for payment or consideration, a court will consider whether the 'service' is sexual in nature and whether the purpose of providing the service is to sexually gratify the person who receives it," Carole Saindon wrote in an email to CBC News.

"Ultimately, it will be a question of fact to be determined by a court, informed by this well-established and binding interpretation by the Supreme Court of Canada."

The committee meets next week to go over the bill clause-by-clause.