A CBC News analysis has found that unions dominate the list of the biggest donors to what are called third parties — organizations or individuals which take part in elections but don't actually run for office or field candidates.

Unions and corporations cannot donate to political parties or local candidates. But they can fund third parties registered with Elections Canada which conduct activities such as election advertising and voter outreach.

CBC News took Elections Canada financial reports from third parties between June 30 and October 1 and analyzed them to find out which have spent the most and received the most donations.

In that period, unions were the source of just over a third of third-party spending.

Unifor alone spent close to $1.3 million on an anti-Conservative ad campaign.

The union's national president, Jerry Dias, said the union is spending this money because the Conservatives have traditionally been hostile toward working-class Canadians and organized labour.

Unifor National President Jerry Dias says the union wants to prevent the Conservatives from returning to power. (Carlos Osorio/Associated Press)

Unifor is not, however, backing any of the other parties explicity, Dias said, noting Unifor does not have "blind loyalty" to either the NDP or the Liberals.

"There's not a ton of differences and ultimately we can live with either, but it's the Conservatives that always pick on working-class people."

The United Steelworkers, who endorse the NDP, spent the second-highest amount, followed by Fairness Works, a third party funded by the Canadian Labour Congress.

According to Elections Canada rules, third parties are allowed to spend $1,023,400 in the pre-election period between June 30 and the start of the election campaign. They can spend an additional $511,700 during the election campaign.

Right-wing third parties

The Conservative-leaning third party that has spent the most is Canada Proud, at just under $200,000, but it had received almost double that amount in contributions as of Oct. 1.

Canada Proud received $100,000 in donations from Alberta businessman Ron Mannix and his investment firm Coril Holdings. Much of its other funding is from individual donations. The money has funded an anti-Liberal ad campaign.

Five other anti-Liberal third parties — Canada Strong and Proud, Quebec Fier, Nova Scotia Proud, Newfoundland Strong and Proudly New Brunwick — are funded almost entirely by the Manning Centre, a Conservative networking organization based in Calgary. Collectively the Manning Centre has given these groups $312,450.

These groups have run some controversial Facebook ads and are the subject of a complaint by Democracy Watch, because the Manning Centre has not disclosed the source of its donations, as is required of other third parties.

Instead of registering as a third party itself, the Manning Centre has funded other groups to attack the Liberals, said Democracy Watch co-founder Duff Conacher, who is calling on Elections Canada to investigate.

Duff Conacher of Democracy Watch says Elections Canada must investigate the third parties funded by the Manning Centre. (Adrian Wyld/CP)

"The Manning Centre is acting as a front for those donors so their secret money can flow into the groups. And the five Proud groups are acting as a front for the Manning Centre because they're spending money that the Manning Centre raised. And Democracy Watch's position is that that's illegal."

Manning Centre donors wanted to fund advertising to balance what they perceived as an abundance of anti-Conservative messaging, spokesperson Troy Lanigan said in a statement.

"We put together some dollars and identified some folks we were confident could make a difference and have an impact."

Lanigan declined to release a list of donors to CBC News.

Democracy Watch's Conacher says third party spending limits should be lowered as they allow special interest groups too much influence.

"They don't need to have as high spending limits as they do, especially given how inexpensive it is to advertise on social media and use email to reach people these days."