A janitorial worker is claiming a contractor paid her under the table for cleaning the prime minister's residence at 24 Sussex Drive.

The worker spoke to The Canadian Press on the condition that she and her employer remain anonymous until she appears at a news conference on Wednesday morning.

A North American union representing service industry workers also says her employer, a major Ottawa-area cleaning contractor, has threatened the woman and her co-workers with dismissal if they try to organize.

In a March 25 letter to the Service Employees International Union, Public Works Minister Rona Ambrose dismissed its written concerns about janitorial procurement practices in federal buildings.

Now the union is filing a complaint to the Ontario Labour Relations Board, alleging unfair labour practices, and to the federal Labour Department, alleging breaches of the Employment Standards Act.

There is no indication that Stephen Harper's family or staff knew about the situation.

An official in the Prime Minister's Office said the contract in question involves only the RCMP post at the gate to 24 Sussex, and not the residence itself.

The official said the residence is cleaned by household staff or, in special cases, the National Capital Commission.

Woman claims to have cleaned residence

However, the woman, an immigrant, said through an interpreter that she did work inside the residence. She told The Canadian Press she dusted and cleaned the living room, among other things.

"I was surprised at how it looked," she said, referring to the interior of 24 Sussex. "It was not as fancy as I expected it to be."

She worked at the residence for a month last November-December.

She said she signed in at the RCMP post each shift before she was taken to the house. Mounties checked her bags and escorted her. She said she never cleaned the guardhouse.

She said between her work at the prime minister's and in another government building, she logged more than 50 hours a week but was never paid overtime.

The payment method was "quite out of the ordinary," she said.

"When she expressed her discomfort with the arrangement she was told it was not possible to pay her through the regular payroll," said Diego Mendez, a union spokesman.

"She refused to work at the prime minister's house soon after."

The woman is still working as a cleaner in a federal building. Her employer has contracts to clean many federal buildings around Ottawa, the union said.

Union brought issue to Public Works

The union brought its broader concerns about cleaning contractors to Ambrose's attention Feb. 25.

In her reply, the minister said a meeting with her "would not achieve your goal" and suggested they take their concerns up with the Human Resources Department.

"To ensure compliance with the Act, PWGSC requires that a statutory declaration be made by the contractor including a specific declaration that he has complied with all lawful obligations with respect to the fair wages and hours of labour regulations," Ambrose wrote.

"Furthermore, for janitorial work in PWGSC-owned buildings — particularly in Ottawa as referenced in your letter — the Department requires that contractors respect the provisions of the Ontario Employment Standards Act, 2000 as applicable to janitorial employees."

Regardless of their obligations, Mendez said some cleaning contractors are increasingly looking for ways to cut corners, resulting in "rampant violations of workers' rights."

"One such method employed by these contractors is by paying cash," Mendez said in an email to The Canadian Press.

In doing so, he said they deny staff basic protections under the Employment Standards Act such as workers' compensation coverage, employment insurance, vacation pay, Canada Pension Plan contributions and sometimes minimum wage.

"They also fail to pay their fair share of payroll taxes," Mendez wrote. "When workers speak up about these violations, they are normally met with threats and intimidation."