The closure of the Indian Point nuclear-power plant in 2021 could cause more reliance by the city on dirty fossil fuels — despite both Mayor de Blasio and Gov Cuomo’s stance in favor of clean energy.

Cuomo last year said that safety measures would cause the early closure of the Indian Point plant, which has history of radioactive leaks and spills.

De Blasio has said he “conditionally” supports the troubled plant’s closure — but a top de Blasio energy aide has said not enough clean energy sources will be available by that time.

“If Indian Point were closing in 2021 we will see localized impacts before these other sources [of clean energy] come online,” Susan DesRoches, deputy director in the Mayor’s Office of Energy, said at a NYU forum earlier this year.

“When you start to look at the reduction of that power locally, we’re also concerned about will there be cost impacts, will there be air-quality impacts.

“And what is the replacement power? It’s heavy intensity on greenhouse gases?”

Asked about DesRouche’s comments, a mayoral spokesman said de Blasio supports Indian Point’s closure as long as the state holds up its end of the bargain.

“The de Blasio administration continues to conditionally support Indian Point’s closure,” the spokesperson said in a statement. “As long as the state mitigates any impacts to the reliability and cost of the replacement power, local air quality and the city’s ability to meet our 80-[by]-50 greenhouse gas emissions targets.”

The reference was to a plan to cut such gases by 80 percent by 2050.

Cuomo seeks to curb greenhouse gas emissions by 40 percent by 2030.

His office defended the plan and dismissed the de Blasio administration’s worries.

“If City Hall has concerns, they could help by starting work on their own clean-energy projects instead of just talking about them,” Cuomo spokesman Rich Azzopardi said.

Azzopardi also said an independent report “made clear that existing projects in the pipeline are more than enough to close Indian Point without reliability issues.”

“To say nothing about our aggressive efforts to develop offshore wind and solar, as well as make our energy grid more efficient,” Azzopardi said.

But state Sen. Terrence Murphy (R-Westchester) whose district includes Indian Point, said, “New York’s hypocritical energy strategy is not prepared to replace the 25% of the region’s energy that will be lost upon closing Indian Point.”

The senator added “I have yet to receive an answer” about the projected cost impact cost on consumers who already among the highest electrical bills in the nation.