OTTAWA - A janitorial worker who says she was paid under the table to clean the prime minister's residence skipped a news conference today where she was to air her complaints.

A spokeswoman with the Service Employees International Union said Zahra Bulle got a late-night call from her employer and got spooked out of appearing this morning.

The single mother of four told The Canadian Press on Tuesday night that she was working for contractor Cleanmatters Janitorial Services Ltd. last November when she took on extra work at 24 Sussex Drive.

She said between her work at the prime minister's house and another government building, she logged more than 50 hours a week and was paid in cash -- but didn't get paid overtime.

Bulle and other workers also claim they were threatened with dismissal by a supervisor if they discussed joining the union.

The owner of Cleanmatters says no employees are ever paid cash and he has never stood in the way of the union's organizing activities.

Gus Zygoumis also says his company has a contract to clean the RCMP guardhouse at 24 Sussex but not the house.

But Bulle told The Canadian Press she had never cleaned the guardhouse, and was working directly inside the residence.

The union is filing complaints with the Ontario Labour Relations Board and the federal Labour Department.

A spokeswoman for the Prime Minister's Office says she expects officials at the Public Works Department will take appropriate action to respond to the complaint.

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