She served as a New Democratic Party member of the Legislative Assembly of Ontario on three occasions between 1975 and 1995 and was a prominent cabinet minister in the government of Bob Rae.
During her time out of political office, she was a member of a City of Ottawa Municipal Energy Planning Project and served as a representative on women's issues for the National Union of Provincial Government Employees.
She was defeated by Progressive Conservative Paul Frederick Taylor in the Ottawa area riding of Carleton East, losing by 240 votes.
[12][13] At the same time during debate on another bill about pay equity, Gigantes was expelled from the legislature for calling Attorney General Ian Scott a liar.
[16] The NDP won a majority government under Bob Rae in the 1990 provincial election, and Gigantes, once again campaigning in Ottawa Centre, defeated Patten by almost 3,000 votes.
[19] In January 1991, Gigantes and fellow cabinet minister Anne Swarbrick led a delegation that appeared before the legal affairs committee of the Senate of Canada that was discussing the bill.
[21] On April 19, 1991, Gigantes resigned from cabinet after inadvertently revealing the name of a Toronto man who had been sent to the United States for drug treatment that wasn't offered in the province.
Gigantes resigned because she allegedly pressured an Ottawa tenant to drop charges against the board members of her public housing project.
"[25][26] The NDP were defeated in the 1995 provincial election and Gigantes again lost the Ottawa Centre riding to Richard Patten by over 1,500 votes.