For months, Bill de Blasio has watched quietly as his old nemesis, former Gov. Andrew M. Cuomo, attempts to stage a comeback by running for mayor of New York City.

But with Mr. Cuomo leading in the polls as the June 24 primary nears, Mr. de Blasio — whose own mayoralty was frequently undermined by Mr. Cuomo — has decided to end his silence.

In a searing interview, Mr. de Blasio said Mr. Cuomo hurt the city as governor, compared him to President Trump and said he was not the proven, competent manager he claims to be.

Mr. de Blasio said Mr. Cuomo lacked the temperament, honesty and integrity needed to effectively run the nation’s largest city.

“He is a vindictive person,” Mr. de Blasio said. “He’s a bully. He’s obsessed with revenge.”

Mr. de Blasio, a Democrat who served as mayor from 2014 through 2021, argued that Mr. Cuomo, who moved to New York City last year, is an outsider who does not understand the city and its needs.

“I had endless conversations with him about what was going on in New York City,” he said of Mr. Cuomo, who was governor for almost Mr. de Blasio’s entire mayoralty before resigning in disgrace.