The two stars, along with West End star Denise Van Outen, will take on judging roles for at least one episode of the new charity talent show that starts on BBC One in the UK on March 14.
The show will continue all week until the finale on March 18 and the girls will judge contestants from around the UK to find the UK's best young Glee club.
Eighteen Glee clubs from across Britain will compete on the show's first night to battle it out for a place in the final nine groups.
The final nine groups will then compete across the rest of the week's shows before the winner is crowned on the Friday night show, where The Wanted will perform.