OTTAWA -- A strike at one of Canada's busiest docks could be coming to an end as the Senate prepares to deal with back-to-work legislation today that would force 1,150 workers back on the job at the Port of Montreal.

The House of Commons approved the bill early Thursday morning, with the Conservatives joining forces with the minority Liberal government, but it must still be passed by the Senate.

Michel Murray, of the Canadian Union of Public Employees' chapter that represents the dockworkers, said the bill is an attack of the workers' constitutional right to strike.

He told the Senate the bill aims to categorize the Montreal port workers as essential workers under economic consecrations but no court in the century has recognized this criteria before.

"In a democratic context, the Charter applies, and we believe that this law is unconstitutional," he said.

Maritime Employers Association President Martin Tessier, who represents the employer, said the bill is not a victory but a failure of the negotiation process.

"All of us in front of you today would have liked a different outcome, but we are at an impasse," he told the Senate.

The Canadian Union of Public Employees, which represents the dockworkers, has said the dispute was sparked when the Maritime Employers Association began imposing extended workday hours without consulting workers.

The union said the employer told workers on April 10 that it would not honour job security provisions in the collective agreement and extended shifts by up to 100 minutes.

The union said workers would have willingly returned to the job had the employer simply ended the scheduling practice.

Murray said his union will challenge the legislation in court if passed by the Senate.

"We do not think the courts will support it," he said

Murray said workers' right to strike is protected under The Canadian Charter of Rights and Freedoms and this right should not to protect the economic interests of their employer.

"We hope that Senators are the guardians of this charter and of its values," he said.

In a 2015 decision on a Saskatchewan case, the Supreme Court of Canada affirmed that the right to strike has constitutional protection.

"The right to strike is an essential element of a meaningful collective bargaining process in our labour relations system," the highest court ruled, noting it also promotes equality in the bargaining process.

Workers at the port have been without a contract since December 2018 and started to refuse overtime and weekend work earlier this month.

The union previously held a 10-day strike in August.

Tessier said the Maritime Employers Association still wants a negotiated agreement with the workers.

"We'll put all our energy toward reaching this goal," he said.