Former City Council Speaker Christine Quinn, an openly gay supporter of Gov. Andrew Cuomo, called Cynthia Nixon an “unqualified lesbian” a day after the actress announced she’s going to challenge the governor in a primary.

In an interview with The Post, Quinn also denounced Nixon for endorsing Bill de Blasio over her in the 2013 Democratic primary for mayor.

“I’m surprised by this race. It’s a flight of fancy on her part,” Quinn said of Nixon’s announcement Monday that she would take on Cuomo in September’s Democratic primary.

“Cynthia Nixon was opposed to having a qualified lesbian become mayor of New York City. Now she wants an unqualified lesbian to be the governor of New York. You have to be qualified and have experience. She isn’t qualified to be the governor,” Quinn said.

Quinn conceded that she and the “Sex and the City” actress both support progressive positions — but added that it takes more than being a reliably leftist celebrity to run the Empire State.

“She’s an accomplished actress, a supporter of political causes and that’s a good thing. Participating in rallies is important,” Quinn said.

“But she’s never run an organization. Being an actress and celebrity doesn’t make you qualified for public office. This is a time to move away from celebrity and toward progressive leadership.”

The former speaker heaped praise on Cuomo, and scoffed at the idea that he should tilt further to the left.

“Gov. Cuomo’s accomplished [a lot] including a $15 minimum wage, opposing fracking and she’s on record supporting the governor on marriage equality,” Quinn gushed.

“Why are we having this primary? Democrats should be united and focusing on winning control of the state Senate and taking back the House of Representatives.”

Nixon brushed off Quinn’s barbs.

“Her being a lesbian and my being a lesbian” is not the issue, she said.

The race, she added, is about “the corruption in Albany. It’s time for an outsider. I’m not an Albany insider.”

She said Cuomo had gotten nearly all of his $30 million in donations from corporate and special interests and virtually none from small donors and grassroots supporters.