Gov. Andrew Cuomo wants comeuppance for the union that led opposition to a proposed Amazon campus in Queens.

In an open letter, the governor's budget director Robert Mujica alleged that the Retail, Wholesale and Department Store Union "probably" engaged in unlawful activities when rallying critics of the aborted Long Island City office complex. The Cuomo appointee's bitter missive lashed out at several parties, including the state Senate, but reserved special vitriol for RWDSU, which has sought to organize both Amazon distribution centers and its Whole Foods grocery chain.

Mujica accused the labor organization of putting its interests ahead of the construction and building services unions that would have benefited from the Long Island City project—and of improperly funding activist organizations that spoke against the deal.

"Ironically, much of the visible 'local' opposition, which was happy to appear at press conferences and protest at City Council hearings during work hours, were actuality organizers paid by one union: RWDSU," Mujica wrote. "If you are wondering if that is even legal, probably not."

The governor's office could not provide the specific names of groups it believed RWDSU illegally financed. The union has in the past given money to New York Communities for Change, which aggressively protested the Amazon plan, but RWDSU's most recent tax filings show no donations to the left-wing organization.

RWDSU hit back at Mujica and, by extension, Cuomo in an equally fierce retort.

"Mr. Mujica's letter is deceitful and dishonest. He is trying to justify a failed process, which was shrouded in secrecy and was crafted without the input of the countless people who would be directly affected," spokeswoman Chelsea Connor said in a statement. "We did not employ community groups to protest. These groups have always stood for our shared principles; not everything is transactional."