“No money was spent to promote an online public service announcement that appeared months ago and was in full compliance with all laws and guidelines,” Mr. Azzopardi said. “No amount of false outrage changes these facts.”

New Yorkers United Together was founded in late March by Steven M. Cohen, a former top aide to Mr. Cuomo; Christine C. Quinn, the former New York City Council speaker; and the public relations consultant Ken Sunshine.

The goal of the 501(c)(3) nonprofit charitable organization, according to documents filed with the New York secretary of state, is to fight discrimination, support diversity and raise money for immigrant legal defense.

“It’s an informal group established in reaction to Donald Trump’s travel ban,” Mr. Sunshine said, referring to the president’s order blocking people from six mostly Muslim nations from entering the United States. “We were discussing what to do, and we came up with this.”

Mr. Sunshine, Ms. Quinn and Mr. Cohen all said the group was planning to do much more in the future, but they declined to give any specifics or to say who funded its creation, whether it would ever disclose its donors or how exactly it planned to support immigrant legal defense. Mr. Siegel declined to say anything.

The group’s first effort, the digital ad, was a 30-second spot featuring celebrities and regular people cheering the diversity and inclusiveness of New York.

“As a New Yorker, I am black,” Mr. Cuomo says in the opening line. “I am white,” Whoopi Goldberg says next, followed by Steve Buscemi, Harvey Fierstein and a dozen other actors and citizens. It ends with a plug for the Liberty Defense Project, a public-private partnership offering free immigrant legal defense.