World's leading authors: state surveillance of personal data is theft
• 500 signatories include five Nobel prize winners
• Writers demand 'digital bill of rights' to curb abuses
• Writers demand 'digital bill of rights' to curb abuses

Clockwise from top left, eight of the people who have signed the petition: Hanif Kureishi, Björk, Arundhati Roy, Don DeLillo, Ian McEwan, Tom Stoppard, Margaret Atwood and Martin Amis
More than 500 of the world's leading authors, including five Nobel prize winners, have condemned the scale of state surveillance revealed by the whistleblower Edward Snowden and warned that spy agencies are undermining democracy and must be curbed by a new international charter.