Comic Lee Evans is also joining cast
The former EastEnders actress will play Lady Christina de Souza in the episode, named Planet Of The Dead.
‘I’m a huge fan of Doctor Who,’ she tells the Daily Record. ‘And I’m very excited to be joining David and the team.’
Comedian Lee Evans will also make an appearance in the one-off show, which is the first of four specials to air this year.
Earlier this week, it was rumoured that Michelle, 24, was in talks with producers to play the new assistant in 2010.