Doctor Who star Jenna Coleman has insisted that she will not reveal whether or not she is leaving the sci-fi show.

The actress, currently on screen with new Time Lord Peter Capaldi, is rumoured to be quitting her role as companion Clara.

But she told Radio Times magazine: "There's lots of rumours. We've sat down with [showrunner] Steven Moffat and we've all decided we don't want anybody to know which way it's going.

"If you know I'm in the next series - or if you know I'm off - you'll know how the story ends."

Asked about the Christmas episode, she added: "Because there's a surprise we've got coming, it's much better that nobody knows which way it's going to go - so that's where we're trying to keep it at the moment... that's all I should probably say."

But she added of her character: "It all becomes rather chaotic, as you can imagine, and that doesn't work at all - it becomes quite impossible."

Capaldi recently insisted that he was "not looking for a new assistant".

"I don't know where these rumours have started," he said. "What I can say is she is absolutely fabulous.

"She's been called upon to do things that I don't think any other companion has had to do, to show a kind of emotional range and I think she's done it absolutely brilliantly."