Toronto city councillor Mary-Margaret McMahon says she will not run in the 2018 municipal election and is calling on other incumbent councillors to step aside too.

The councillor for Ward 32, Beaches-East York, first won her seat in 2010 with a promise that she would only serve two terms in the position.

At a news conference Monday at city hall, McMahon confirmed her campaign pledge.

"My name will not be on the ballot for 2018 because I truly believe in democratic reform," McMahon told reporters.

McMahon has been a vocal advocate for term limits, arguing that they would lead to more diversity on city council and lower the barrier to entry for aspiring municipal politicians.

"I believe term limits are healthy for a city, for neighbourhoods, and for politicians," she said. "I believe being a politician is a public service, not a career."

During her seven years as a councillor, McMahon has brought two motions to city council calling for term limits, but both were defeated. She has also supported ranked ballots, the redrawing of ward boundaries and other measures to increase voter turnout.

Toronto City Council

38 out of 44 incumbent councillors ran for re-election in 2014. (David Donnelly/CBC)

With little progress on the city council floor, she's now making an appeal to other incumbent councillors to step aside on their own accord — but hasn't specified how long she believes councillors should be in the job.

"I would encourage my councillor colleagues to think of their accomplishments, to think about their futures, and to take the torch and pass it on to someone else," she said.

Incumbents respond

Unsurprisingly, some of the city's longest-tenured councillors say they're staunchly opposed to mandatory service limits.

"I think term limits are very undemocratic, it's governments telling you who you can't vote for," said Ward 9 Coun. Maria Augimeri, Toronto's most senior councillor with 32 years of continuous service.

"I don't see why my run ought to be impeded by a law telling my constituents who have been so loyal to me over the last 30 years that I can no longer represent them," she told CBC Toronto.

John Filion, who has served on the former North York and Toronto councils for the past 26 years, said it should be up to voters to determine if an incumbent councillor deserves another chance.

He says that decision depends on the person in office, not how long they've been there.

"I can point to very long term councillors who are doing a great job, who hit the refresh button every year," he said. "And then I could point to other people who have been around a very long time and are past their best- before date."

Coun. Maria Augimeri

With 32 years of experience, Coun. Maria Augimeri is Toronto's longest serving councillor. (CBC)

Experience or fresh blood?

When McMahon was first elected in 2010, she was one of 15 new councillors to win a seat in the council chamber.

"We brought a breath of fresh air to city hall and we came up with new ideas, we had new energy and no baggage," McMahon said.

However, the long serving councillors say their institutional memory and ability to doggedly pursue long-term projects would be lost with the more frequent turnover caused by term limits.

Augimeri points to a fight with Toronto Hydro over the construction of the Jane/Sheppard Library in her ward as an example.

"It took me 11 years to have that library built and another five years to have the grounds around it declared as a park," Augimeri said."How could a short-term councillor accomplish truly great things for her community?" she asked.

Augimeri said she's likely to run for re-election again in 2018.

Meanwhile, McMahon said she will continue her city-building work from outside city hall.

Toronto's longest serving city councillors

Maria Augimeri, Ward 9: 32 years

Frances Nunziata, Ward 11: 29 years

John Filion, Ward 23: 26 years

Joe Mihevc, Ward 21: 26 years

David Shiner, Ward 24: 26 years

Denzil Minnan-Wong, Ward 34: 23 years