David Walliams, Stephen Fry and The Saturdays are supporting David Cameron's pledge to change the law to allow gay marriage, via the social media-based Out4Marriage campaign.

Announced on Twitter by Fry last Tuesday, the initiative has been growing throughout the week, with a host of names including James Corden and David Walliams tweeting their support of gay marriage and The Saturdays posting an Out4Marriage video on YouTube. UK publications including Attitude and Gay Times are sponsoring the campaign.