The elections watchdog said the New Democrats broke the rules after accepting an unspecified amount of sponsorship money from large unions during the NDP's national convention last June.
For example, an evening dinner with late leader Jack Layton and Nova Scotia Premier Darrell Dexter was sponsored by the Public Service Alliance of Canada.
Elections Canada noted that the sponsorships constituted contributions, and because parties can't accept contributions from unions, the money was considered ineligible.
Accepting money from unions or corporations isn't always a violation — they can pay parties for goods or services, such as advertising or a sponsorship, as long as there is an actual market they are accessing and that they pay an appropriate market value.
Paying more than market value equals contributing politically to the party.
The Canada Elections Act says such contributions must be paid back to the donor, or to Elections Canada, which then sends it to the receiver general.
Reporters asked Mulcair how much the party had paid back to the unions — which included the Public Service Alliance of Canada and the United Steelworkers.
Mulcair would offer no details.
"Elections Canada is very clear that unlike the Conservatives, we respect Elections Canada, we continue to work with them, and we continue to be in conformity with the law," Mulcair said Wednesday following the NDP's weekly caucus meeting.
"We continue to obey the law, that's what Elections Canada confirms in the letter."
Later, NDP House leader Nathan Cullen also said he couldn't specify how much money was paid back. The details will be made public when the NDP files their quarterly financial results with Elections Canada sometime in the summer.
"These are guys who continually play the game out of both sides of their mouth," said Public Safety Minister Vic Toews.
"They demand accountability, but show no accountability themselves."
The details of the violations were revealed in a letter sent to the Conservative Party of Canada last week. The Tories had lodged a formal complaint with Elections Canada last August.
They also held a day of committee hearings on the sponsorships last October.
This is the second time in a year the NDP have run afoul of the Canada Elections Act.
The Commissioner of Canada Elections had found last fall that the NDP solicited funds on behalf of another entity — a no-no under Canadian law.
The NDP had taken in donations to commemorate Layton's death to be passed on to the new Broadbent Institute think tank. It also promised to issue tax receipts. Ultimately, it had to return money to donors and set up an another system for contributions to be routed to the institute.
The Conservatives have also come under the Elections Canada microscope.
In March, the party paid back Elections Canada $230,198 and dropped an appeal at the Supreme Court. The case involved the funnelling of national funds to local ridings that in turn paid for national advertising in the 2006 election —a practice that caused the party to exceed its legal spending limits.
The party also settled last November for another $52,000 over a separate set of regulatory charges related to the so-called "in and out" scheme.
The electoral watchdog has also been probing allegations of voter suppression during the last general election. The Conservatives have acknowledged some irregularities in one Ontario riding, but there is no evidence directly linking the party to misleading "robocalls."
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