The London daily newspaper included a picture of the actor, popularly known as Barry from EastEnders, performing as the rock legend on Stars in their Eyes.
Williamson appeared on the now defunct ITV entertainment show as the 'Bat Out of Hell' singer in a 2004 soap star special.
The blunder has been widely ridiculed on social networking site Twitter.
After leaving EastEnders, Williamson played himself in Ricky Gervais/Stephen Merchant sitcom Extras.
The 46-year-old will star in a spinoff to one of Gervais's latest comedies, Life's Too Short, alongside Les Dennis.