Mayor Bill de Blasio on Monday joined a groundswell of support for permanently banning serial transit pervs from riding subways and buses.

“If someone is a threat to others — as long as it’s done while respecting constitutional rights — I think it’s a real proposal that needs to be looked at,” Hizzoner told NY1’s “Inside City Hall.”

“Many [straphangers] are anxious knowing that there are folks around that might mean them harm,” he added. “If we can help ensure that it’s done constitutionally, I think that’s an idea that has some real merit.”

Last week, the NYPD said that transit serial sickos who are convicted of transit crimes more than once could be banned from the subways and buses permanently. And earlier this month, Gov. Andrew Cuomo also came out in favor of such a ban.

The Post last week exclusively reported that cops nabbed James Hunt — one of the “Dirty Dozen” repeat offenders who has scores of arrests for subway sex crimes — at the 42nd Street Bryant Park station for groping a 13-year-old girl who was buying a MetroCard.

Hunt, who allegedly likes to masturbate in front of commuters while sucking his thumb, had previously racked up at least 78 arrests, including 32 for transit sex crimes, according to sources.