Sid Ryan, president of the Ontario Federation of Labour, which represents 54 unions, says his organization will redouble efforts to make sure Prime Minister Stephen Harper's Conservatives don't win October's federal election.

The federation's leader is upset with the passing of Bill C-377, the Conservatives' controversial private member's bill that forces labour unions to publicly disclose how they spend their money.

The bill, sponsored by Conservative MP Russ Hiebert and backed strongly by the Prime Minister's Office, gained Senate approval Tuesday and requires unions to publicly disclose any spending of $5,000 or more and any salary of more than $100,000.

Unions will have to provide that information to the Canada Revenue Agency, which would publicly post the information to its website.

Conservatives argued the bill will shed light on union finances.

Ryan called it "a blatant attack" on unions.

"It's punitive. Nobody else is expected to do this," he said.

Ryan claims Conservatives argue that not all members of a union share a common, agreed-upon political view and that unions are using dues to mount political action campaigns members may not agree with.

"What it's trying to do is create internal strife in the labour movement itself," Ryan said of the bill.

He admitted unions will campaign against the Conservatives this fall.

"We'll redouble our efforts to make sure Harper doesn't get re-elected," he said.

Ryan claims the new law will force unions to hire auditors and bookkeepers that aren't necessary. Union books are open to the membership, but not necessarily the public.

"It's so ridiculous. We have to account for every $5,000 expenditure we've got. It doesn't matter what it is, we have to account for it," Ryan said.

The $5,000 expenditures could include new roofs, furnaces and political contributions.

'Transparency' necessary, group says

A group that lobbied for the Senate to pass the bill applauded the final vote Tuesday.

"Transparency and accountability are fundamental to democracy," Terrance Oakey, president of Merit Canada, said in a statement. "If labour organizations want to enjoy the dual benefits of mandatory dues collection and beneficial tax treatment, they must earn it by operating in a transparent manner."

The bill covers all "labour organizations,"or any organization formed for purposes including the regulation of relations between employers and employees:

Organized groups.

Federations.

Congresses.

Labour councils.

Joint councils.

Conferences.

General committees.

Joint boards of such organizations.

Former Conservative senator Hugh Segal, who opposed the bill, had previously told The Canadian Press that the passage of C-377 could hurt the Conservatives in dozens of ridings where labour unions could influence the outcome of the fall vote.

"Why somebody would decide that kind of suicidal, ideologically narrow excess is in the national or the party's interests or the prime minister's interests is completely beyond me," Segal said in an interview last week.

In a statement Tuesday, minutes after the final vote on C-377, Liberal Leader Justin Trudeau vowed to repeal the law should his party form the next government.

The NDP has also pledged to repeal the bill if it forms government.