Jenna, who got her big break as a young actress in Emmerdale, said she was happy to be filming another series as Clara Oswald.
She said: “It’s wonderful. I get a whole other series of stories with the Doctor and I think for me I couldn’t walk away with the story being unresolved and there is so much more to do.
“I think they’ve finally just reached a point where they really understand each other.
“The arrival of the 12th doctor has just kind of dropped this whole bombshell and allowed the dynamic to totally change, so I think just when Clara was feeling more comfortable in the relationship, it has suddenly thrown something new up.”
Fans of the show were kept guessing by the Christmas Day special which hinted her character was on her way out, before revealing she was set to stay.
Peter, who became the 12th Time Lord last year, said he was “excited and delighted” that Jenna had signed up for another stint as his companion.
He said: “I’m thrilled. Jenna has just been fantastic and such a pleasure to work with.”