NEW YORK (CBSNewYork) — City Comptroller Scott Stringer offered a stinging assessment of Mayor Bill de Blasio’s fundraising apparatus Thursday – labeling it nothing more than a slush fund.

Stringer launched the attack on the mayor’s controversial fundraising arm – the Campaign for One New York.

“This slush fund never should have been constituted,” Stringer said.

But Stringer did not stop there. He referred to a decision on Wednesday by the Campaign Finance Board, which said that while de Blasio did not break the law, he used a loophole that raised serious perceptions of pay to play.

“The standard should be whether you broke the law,” Stringer said. “The standard should be, what’s the best practice for conducting political campaigns?”

De Blasio, who has steadfastly maintained he followed the guidance of lawyers in doing what he did, was clearly not happy with the comptroller’s attack.

As WCBS 880’s Rich Lamb reported, his honor was uncharacteristically blunt.

“My reaction is he doesn’t know what he’s talking about,” de Blasio said of Stringer.

When asked about Stringer’s motivations, de Blasio had little comment.

“As to the comptroller’s personal motivations or what they are, I’m not going to conjecture,” de Blasio said. “He just has his facts wrong.”

De Blasio also defended his own record.

“We’ve been very clear – a fully disclosed effort to achieve pre-K for all our children and affordable housing for half a million New Yorkers and fully disclosed, and again, I think this is where the line should be drawn,” the mayor said.

Stringer is among those being talked about as a potential de Blasio challenger in 2017.