Saturday's edition of The Sun reports that former Hollyoaks actress Elize Du Toit has been cast in Series Three.
It says the 25-year-old is to play the character Miss Dexter but does not reveal which story she will be in.
The article features spoiler information about Dexter as well as another character in the forthcoming series (although they are not necessarily in the same story). Click on the tag below to read more and for the link to the Sun story.
The Sun says: "The 25-year-old - who was sex bomb Izzy in the Channel 4 soap - will play baddie Miss Dexter.
"An insider said: 'She is an extremely sinister character who clashes with the Doctor after setting a trap for him.'
"Meanwhile actor Michael Sheen, who played Tony Blair in Oscar-nominated movie The Queen, is battling with Life On Mars star John Simm to play The Master."