OTTAWA -- Green party leadership voiced their displeasure Monday morning with other parties not standing down on running candidates in the upcoming Toronto Centre byelection, where newly-named Green Leader Annamie Paul is campaigning.

Paul was named the new leader of the federal Green Party at an event in Ottawa on Saturday, after a competitive and mostly-virtual leadership race. She is running to win what would be the Green Party’s fourth seat in the House of Commons in an Oct. 26 byelection that was called by Prime Minister Justin Trudeau to fill the seat left vacant by former finance minister Bill Morneau.

Citing what's known as a "leaders' courtesy" – a historic but now rarely applied parliamentary convention that parties opt not to run candidates in byelections where another party’s leader is running — both Paul and Green Party parliamentary leader Elizabeth May said they are neither surprised nor happy.

Their criticism focused particularly on the NDP, after the Greens chose not to run a candidate against NDP Leader Jagmeet Singh in his 2019 Burnaby South byelection.

"He might have lost," said May of Singh's race last year and the perceived impact of not putting up a Green opponent. Singh won the riding with 39 per cent of the vote, beating out challengers from the other major federal parties.

May said at the time when she extended the courtesy to Singh — a then newcomer to the federal stage — he said it was a "very classy thing" to do.

"So I'd like Jagmeet Singh to think about it. I'd like New Democrats to reach out to him and say 'How classy is it to try to block the entry to the House of Commons of the first black woman leader of a federal political party?'" May said.

Despite this, the NDP have already nominated their self-described queer and racialized candidate — artist and community organizer Brian Chang — who came second to Morneau in the riding during the 2019 general election. Paul also ran in that campaign, and placed fourth.

"A few great candidates decided to put their names forward to run for the NDP nomination in Toronto Centre and NDP members democratically chose Brian Chang to represent them," said NDP National Director Anne McGrath in a statement.

The Liberals had already bucked a pledge for open nominations by appointing their candidate — former CTV broadcaster Marci Ien — when the campaign was called.

The Liberals have held the riding since 1993, and party spokesperson Braeden Caley confirmed that Ien will remain in the race.

" We congratulate Ms. Paul on her election as Green Party leader and wish her well as her party's candidate in the riding, and Marci Ien’s campaign in Toronto Centre is looking forward to a positive contrast of ideas with all of the other parties,” Caley said in an email.

Paul criticized the prime minister for calling a pandemic byelection in the smallest riding of the country, where the COVID-19 case count is spiking, saying it will be "difficult for people to exercise their right to vote in a safe way."

She said she knows she's in for a tough race.

"I'm a first, and as a first you're accustomed to fighting, you're accustomed to have to overcome every single barrier, to get to where you're trying to go to. You know, if we have to do that yet again in Toronto Center then we're prepared to do that. They won't stand down, but I'm going to stand up for the residents of Toronto Centre," Paul said.

According to Elections Canada, the People's Party of Canada, the Free Party Canada, and an independent candidate named Above Znoneofthe are registered candidates in the race. The Conservatives say their pick, Benjamin Sharma, is in the process of getting on the ballot.

This campaign is one of two Oct. 26 byelections, with the other taking place in the Toronto riding of York Centre.