British actor David Tennant insists Doctor Who would be ruined if the Timelord and his assistant ROSE started a steamy affair.

Tennant, who plays the Doctor in the cult BBC show, refuses to allow the writers to introduce anything other than the most innocent romance into the cult series.

He says, "The story between the Doctor and Rose is basically a love story without the shagging (sexual intercourse).

"That's certainly something we will continue to explore. But it's still absolutely celibate. I think that's very important.

"As soon as there's nookie in the Tardis, it would all go wrong."