Utah Jazz center Jeff Withey says he NEVER got physical with his Playboy Playmate ex-fiancee, Kennedy Summers ... claiming she made the whole thing up to damage his reputation. 

As we previously reported, Summers -- the 2014 Playmate of the Year -- filed a police report earlier this week accusing Withey of domestic violence in an alleged 2016 incident.

Now, Withey's attorney, Alan Jackson, is firing back with a very strong denial.

"These salacious and patently false allegations appear to be nothing more than a vicious and calculated attempt by an angry former girlfriend to damage Mr. Withey’s good reputation," Jackson says.

"It is no coincidence that these fabricated claims conveniently come during the middle of the NBA playoffs, or that TMZ and the police department were notified on the same day."

"There is no truth to the accusations, and when the facts come to light we are confident that the falsity of the claims, and the true motivations of the person behind them, will be exposed."

Cops are investigating the allegations. No arrests have been made and no charges have been filed.