Rumours have been swirling that Ross would be coming back for the special episodes next month alongside Barbara Windsor, who plays Grant's mum Peggy Mitchell.
However, Ross has now confirmed that he won't be reprising his role - at least not for now.
"I can't join her [Barbara]," he revealed to the Gloucester Citizen. "It's just about space in my diary - although I would never rule out going back to EastEnders, I owe it a heck of a lot. I think it's a great show."
Extreme World presenter Ross originally left the long-running BBC One soap in 1999 after playing his character for nine years. He returned for a year in 2005.
EastEnders' anniversary week episodes are set to start on 16 February, and viewers will finally find out who killed Lucy Beale (played by Hetti Bywater) following her mysterious murder last Easter.
The soap will air a special flashback episode, seeing the return of Lucy, Rainie Cross (played by Tanya Franks) and Jake Stone (Jamie Lomas).
Aside from the return of Peggy Mitchell, the anniversary special will also welcome back Tanya Branning, played by Jo Joyner.
EastEnders will air a special 30-minute live episode during their anniversary week, while all other episodes will feature live elements.
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