By Tuesday evening, more than 10,000 people had already signed up to the campaign, a spokesman for Privacy International told The Intercept.
In a statement announcing the campaign on Monday, Eric King, deputy director of Privacy International, said: “The public have a right to know if they were illegally spied on, and GCHQ must come clean on whose records they hold that they should never have had in the first place.
“We have known for some time that the NSA and GCHQ have been engaged in mass surveillance, but never before could anyone explicitly find out if their phone calls, emails, or location histories were unlawfully shared between the U.S. and U.K.
“There are few chances that people have to directly challenge the seemingly unrestrained surveillance state, but individuals now have a historic opportunity finally hold GCHQ accountable for their unlawful actions.”