I haven't seen/heard the interview myself, but I'm sure that Tennant was doing no more than echoing the conventional wisdom that there was no hanky panky in the TARDIS prior to 1996, and was certainly speaking about the character, not the actor. Jon Pertwee himself described the character of the Doctor as being "asexual" in an interview that gets routinely trotted out whenever anyone wants to disparage recent regenerations' penchant for snogging.*
But since Sean Pertwee seemed possibly genuinely distressed at the idea that the world might not recognize his father's status as a sex god, I will step up and reassure him that this is not a problem. Not from where I'm standing, anyway.
* These people somehow never mention that Pertwee's doc still wins in the "Doctor most likely to get handcuffed to a pretty girl" category, which, I think, problematizes the asexuality argument a bit.
ETA: I've now seen the BBC Breakfast interview, and the word "sexless" was never uttered. The interviewer suggested that Tennant had done "a lot of snogging", Tennant questioned the use of the word "a lot", and then conceded that he had done "more than Jon Pertwee." Sheesh.