Playboy mogul Hugh Hefner has taken to Twitter to defend his reputation as a lothario after his ex-fiancee, Crystal Harris, said sex with him only lasted two seconds.

The 85-year-old champion of sexual expression tweeted: "Crystal lied about our relationship on Howard Stern but I don't know why. Maybe a new boyfriend?"

He also tweeted another fan, telling them his 25-year-old former lover was a liar.

"Crystal convinced me that she adored me. That was the first lie."

Harris broke off the engagement to Hefner last month – a week before their planned wedding – and then revealed they had only had sex once

She spilled the details on th eone-time event to US shock jock Howard Stern yesterday: "I was like, "Ahhh." I was over it. I just like, walked away. I'm not turned on by Hef, sorry."

"He doesn't really take off his clothes," she added about her former lover.

"I've never seen Hef naked."

Hefner previously said he never saw the split coming.

 "I think an argument could be made that she took me for a ride, but I must say, quite frankly, it was a pretty nice ride. If she was faking it, she did it very well.