Eight US lawmakers have withdrawn their backing from anti-piracy laws, amid “blackout” protests on thousands of internet sites.

Two of the bill’s co-sponsors, Marco Rubio from Florida and Roy Blunt from Missouri, are among those backing away.

Online encyclopaedia Wikipedia and blog service WordPress are among the highest profile sites to block their content.

The Motion Picture Association of America (MPAA) has branded the protests as “irresponsible” and a “stunt”.

The MPAA, Hollywood’s primary advocate in Washington and a key supporter of the legislation, is led by former Connecticut Democratic Senator Chris Dodd.

Both bills focus on responding to online piracy, specifically illegal copies of films and other media.

The bills would also outlaw sites from containing information about how to access blocked sites.