The largest private sector union in Canada said Wednesday it is splitting with the Canadian Labour Congress over issues which include disagreements about the rights of workers to choose what union should represent them.

In a notice posted on its website, Unifor national president Jerry Dias and Quebec director Renaud Gagne said the congress has also been less than supportive of their concern about American-based unions "trampling on the rights" of workers.

Unifor said its national executive board voted unanimously Tuesday to discontinue its membership in the CLC, the national lobby group for Canada's labour movement, effective immediately.

<a href="https://twitter.com/hashtag/Unifor?src=hash&ref_src=twsrc%5Etfw">#Unifor</a> has decided to disaffiliate from the Canadian Labour Congress due to inaction on U.S.-based unions trampling the rights of Canadian workers to choose representation or express dissent. <a href="https://t.co/KZcResfceS">https://t.co/KZcResfceS</a> —@JerryPDias

"In light of the ongoing lack of action and will by the affiliates of the Canadian Labour Congress to address the aggressive and undemocratic tactics shown by U.S.-based unions towards workers in Canadian locals, a decision was made by the leadership of our union ... to discontinue Unifor's affiliation and membership," the notice said.

"Our union is opposed to any union that threatens, harasses, intimidates or silences workers for simply asserting their democratic rights to choose a union or for the purpose of quelling dissent within the local."

In a separate letter to CLC president Hassan Yussuff posted on Unifor's website, Dias said Unifor's request to join a CLC committee studying the issue of workers' rights to switch unions has been ignored, adding it's "unfathomable" that the largest private-sector union wouldn't be part of that work.

He also said that the CLC has failed to deal with two instances of U.S.-based unions interfering in elections for Canadian union local leadership.

The CLC did not immediately respond to a request for comment.

Mark Hancock, national president of the Canadian Union of Public Employees, which is the CLC's largest public union member, and Charles Fleury, CUPE's national secretary-treasurer called the split between Unifor and the CLC "regrettable."

"It is our view that whatever difficulties led to Unifor leaving the CLC should not be insurmountable ones, and we encourage their leadership to sit down with representatives of the CLC and try to work out those differences, for the good of the labour movement," Hancock and Fleury said in a statement.

Larry Savage, chair of the department of labour studies at Brock University, tweeted that Unifor's decision to leave the

CLC "will definitely shake things up in the Canadian labour movement."