A 17-year NYPD veteran assigned to Mayor Bloomberg’s security detail was charged yesterday in the shooting of his girlfriend’s ex-boyfriend.

Leopold McLean, 46, pleaded not guilty to a 20-count indictment, including second-degree attempted-murder charges, for allegedly shooting LePaul Gammons in the buttocks as Gammons tried to flee the raging officer.

Gammons, 39, was violating an order of protection filed by the woman when he showed up at her Queens home last Nov. 12, authorities said.

McLean — who is free on $10,000 bail — allegedly told NYPD Internal Affairs investigators that Gammons attacked him with a knife and he was forced to shoot.

But forensic investigations revealed that Gammons was shot from behind.