VICTORIA, B.C. - A coalition of B.C. unions says it will take its fight against proposed changes to the election act to court.

Seven B.C. unions and the B.C. Federation of Labour say they will launch a lawsuit against revisions to the provincial election law that will limit how much third-party groups can spend on an election campaign.

Angela Schira, secretary-treasurer of the federation, said the lawsuit will argue that the legislation is an infringement on the public's constitutional right to free speech.

"This gag law really isn't enhancing any democracy. It's silencing critics, or people who may speak out about government issues,'' she said in an interview Thursday.

"Why would you limit any discussion anyone in the public may have about their government?''

Schira said the lawsuit against Bill 42 is slated to be filed in mid-July.

The so-called election gag law, as it's known among critics, places spending limits on third-party advertising during the 28-day campaign and for 60 days prior to the writ being dropped.

Third-party groups can spend $3,000 per riding, or $150,000 maximum, in that period.

Despite an outcry from the Opposition New Democrats, the Liberals used their majority muscle to invoke closure and push the bill through the legislature on its final day this spring.

British Columbia has a fixed election date and voters will go to the polls on May 12, 2009.

Schira questioned the rationale of limiting third-party advertising when political parties can engage in a free-for-all in campaign spending.

"If you don't do yourself, why would you do just your critics?'' she said.

Schira was unable to say how much the federation spent in advertising during the 2005 provincial election campaign.

The spending limit mirrors a similar federal law.

The Canada Elections Act limit how much a third-party group can spend on advertising during the 28 days of a federal election campaign. The limit rises annually with inflation, and now stands at $183,000 total, or $3,666 in each riding.

Stephen Harper twice tried to challenge the changes to the federal law as unconstitutional in the Supreme Court before he became prime minister -- once in 2000, when he was head of the National Citizens' Coalition, and again in 2004, as leader of the federal Conservatives.

Harper said the limits infringed on freedom of expression and of the voters' right to be fully informed.

In both instances, the Supreme Court of Canada ruled against him.