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OTTAWA, Ontario (AP) — Some 155,000 federal workers, including 35,000 from Canada’s tax agency, went on strike after midnight on Wednesday in what their union is calling one of the largest strikes in the country’s history.

The Public Service Alliance of Canada said the strike was called after talks with the government failed to produce an agreement. Picket lines will be set up at more than 250 locations.

The strike involving the Canada Revenue Agency comes as tax returns are due.

Chris Aylward, the union’s national president, said the bargaining teams would remain at the table throughout the strike.

“The Government has done everything it can to reach a deal and avoid disrupting the services that Canadians rely on. Despite some ongoing movement at the bargaining table on key issues by both sides, the Public Service Alliance of Canada (PSAC) has decided to proceed with a nation-wide general strike,” the federal government’s Treasury Board said in a statement.

Wage increases are the main issue.

The Treasury Board said it offered the union a 9% raise over three years on the recommendation of the third-party Public Interest Commission.

But the union has pushed for annual raises of 4.5% over the next three years, arguing the increases are necessary to keep pace with inflation. It has also kept issues such as greater limits on contract work, more anti-racism training and provisions for remote work on the table.

Mediated contract negotiations between the Public Service Alliance of Canada and the government began in early April and continued through the weekend in what the union describes as the government’s last chance to reach a deal.