Michelle Keegan auditions for the role of Father Christmas at Downton Abbey in a Text Santa special.

Michelle Keegan

Michelle Keegan

The former 'Coronation Street' actress is one of a number of stars who will be seen auditioning for the part in front of Hugh Bonneville's Lord Grantham and Penelope Wilton's Isobel Crawley in the upcoming charity sketch.

Sir Bruce Forsyth shows up to his audition wearing a top hat and carrying a cane, fashion guru Gok Wan arrives with a Santa outfit and measuring tape and Gordon Ramsay sticks to his usual all-white chef's outfit in the festive special.

'Harry Potter' actors Jim Broadbent and Warwick Davis complete the line-up of stars auditioning for the coveted role of Santa Claus while actress Brenda Blethyn turns up in character as DCI Vera Stanhope from 'Vera', announcing she's there to "investigate a murder".

Celebrities are invading ITV's top television programmes on December 18 for a three-hour special as part of the charity campaign Text Santa.

Elsewhere, Joan Collins will appear in a 'Benidorm' sketch following her guest role in the show in 2014, while 'Coronation Street' actors will be seen morphing into characters from the soap's past in a 'Back to the Future' crossover.

The sketches will all feature on a live show hosted by Christine Bleakley, Alesha Dixon, Caroline Flack, Amanda Holden, Paddy McGuinness, Stephen Mulhern, Olly Murs, Philip Schofield and Holly Willoughby.

Viewers will be encouraged to donate via text in support of Macmillan Cancer Support, Make-A-Wish UK and Save the Children.

Films about the charities will be presented by Ant & Dec, Bradley Walsh, Julie Walters, Martin Clunes, Amanda Holden and Myleene Klass.

Little Mix are set to perform, as well as the winner of 'The X Factor'.