Last May the B.C. Liberal government set spending limits for third parties at $3,000 in a single electoral district and $150,000 provincewide for the 88 days before an election. (Sam Bufalini/CBC)

A controversial B.C. law that restricts third-party spending on political advertising during the coming provincial election kicks in on Friday, but critics continue to say it's a threat to free speech.

The law limits election advertising by any person or organization that is not a political candidate, riding organization or party to $3,000 in a single electoral district and $150,000 provincewide for the 88 days before an election.

It's been attacked by the NDP Opposition and the B.C. labour movement, which sponsored a full-page ad in major newspapers on Thursday calling for voters to speak out in protest.

New Democrat MLA Leonard Krog said he's already heard from community groups who are concerned they might not be able to even sponsor a public forum during the election campaign.

"It is essentially having a real chill on public discussion," said Krog on Thursday.

"It means we are going to virtually criminalize behaviour which is the fundamental foundation of any democratic society," he said.

Liberals defend restrictions

But Liberal MLA Wally Oppal defended the legislation, still known as Bill 42, the name it had before it came into effect last May, saying it would be unfair to voters to allow outside groups to spend as much as they want to influence the election's outcome.

"I think we've gone over these arguments before as to whether or not we want undisciplined spending by third parties who may be in a position to hijack elections," said Oppal on Thursday.

B.C. voters go to the polls on May 12 under the province's fixed-term election system, and in the run-up to Friday's deadline, interest groups on both sides of the political spectrum have flooded the airwaves with ads.

VoteSmartBC, a group representing non-union construction contractors, attacked the economic record of previous NDP governments.

Unions meanwhile hammered the governing Liberals for their record in areas such as health care and education.

But as of Friday, those ads will end, unless they fit within the strict limits imposed by the law.

Court injunction failed

B.C.'s labour unions tried unsuccessfully to have the law suspended in court before the coming election, while they await the outcome of their constitutional challenge against what they argue is an infringement of charter rights to free speech and association.

But a B.C. Supreme Court judge dismissed their injunction application in December, saying their complaints don't outweigh the law's intended benefits.

Suspending the law before the larger constitutional question is settled would upset the balance the legislation currently strikes, said Justice Frank Cole.

Cole pointed to current Prime Minister Stephen Harper's challenge of the federal third-party spending law in 2000, when he headed the National Citizens Coalition lobby group.

The Supreme Court of Canada rejected his request for a temporary injunction, saying it would prematurely decide the main issue.

Harper lost his constitutional challenge in 2004, but since taking power has not abolished the law.

Law dates back to 1995

B.C.'s spending limits legislation dates from 1995, but was challenged successfully by the publisher of the Vancouver Sun and Province newspapers.

The B.C. Liberal government then amended the law last May.

Elections BC rules define election advertising to include messages that take a position on an issue that is associated with a candidate or registered political party.

The rules, however, exclude messages sent directly to members of the ad sponsor's group, employees or shareholders, and personal political views sent by individuals on a non-commercial basis, including text messages, phone calls and the internet.

With files from the Canadian Press