TORONTO - One of Canada's largest unions announced Monday it has filed a complaint with the United Nations against the Ontario government for preventing farm workers from forming labour unions.

The complaint by United Food and Commercial Workers Canada to the UN's International Labour Organization in Geneva argues that Ontario's ban on farm unions is unconstitutional and violates the human rights of farm workers.

"The government of Ontario needs to recognize that labour rights are human rights," said union president Wayne Hanley.

"For Ontario to continue to delay and deny the rights of agriculture workers is an international shame."

In November, the Ontario Court of Appeal tossed out a provincial law that effectively prohibited farm workers from unionizing, but the Ontario government has asked the Supreme Court of Canada to overturn the decision.

Ontario Agriculture Minister Leona Dombrowsky refused repeated requests from reporters Monday to explain the province's objection to farm unions.

"I'm going to ask you to understand that we are waiting for the court to decide this," Dombrowsky said.

"Our side is that we have asked the court to make a decision on this ... because we are aware that there is more than one perspective on this."

In the legislature, the New Democrats also tried unsuccessfully to get the Liberal government to explain why it won't allow farm workers to unionize, and angrily dismissed claims by Dombrowsky that she couldn't comment because the issue is before the courts.

"The only reason it's before the courts is because this government is dragging it before the courts again instead of doing the right thing by farm workers in this province," said NDP Leader Andrea Horwath.

"Why is this government denying a fundamental right to some of Ontario's most exploited and vulnerable workers?"

Horwath tried putting the question to Premier Dalton McGuinty, who deflected it to Labour Minister Peter Fonseca, who said there were "issues" from the Court of Appeal ruling that the province wanted the Supreme Court to decide.

"We feel that these issues need to be looked at, and the Supreme Court will be able to do that," said Fonseca, who did not elaborate on the issues.

The United Food and Commercial Workers said it has also made arguments to the Supreme Court about why the province's leave to appeal should be denied.

The Supreme Court is expected to decide on whether to hear the province's appeal later this spring.