New York City Comptroller Scott Stringer blasted Mayor Bill de Blasio’s housing policy as fuel for gentrification Wednesday, but experts raised questions about his own plan for affordable housing.

“This is a broken system. But instead of fixing it, we keep doubling down because we’re told this is the best we can do,” Stringer said. “I refuse to accept that.”

Stringer called for an expanded affordable housing mandate that would cover all new developments — even those without government subsidy or additional height to build more market-rate units.

Additionally, he demanded an end the state’s controversial 421a policy that provides developers with massive property tax breaks for including affordable units in their developments.

He said the change would provide up to $1.6 billion in new revenue for the city’s affordable housing program.

“The economics of it are challenging,” said Sean Campion, a top analyst with the Citizens Budget Commission.

“The inequities of the property tax system are such that it is nearly impossible to build rental buildings because of the tax rates.”