Nick Clegg sounded the death knell of the controversial snoopers' charter today, during a radio phone-in show which left listeners reeling.
Without any advance notice, the deputy prime minister suddenly said the communications data bill would not be passed while the Liberal Democrats are in government.
"The snoopers' charter isn't going to happen," he said.
"It won't happen while Lib Dems are in government.
"Of course we need to support police, they have significant powers already which I support them in using.
"This idea of a snoopers' charter - I think it isn't workable or proportionate. It isn't going to happen."
The move will be a massive relief to civil liberties groups and privacy campaigners, who had long opposed plans to hand details of users' internet use to intelligence agencies and police.
The bill would have recorded every website visit, email and social media interaction by every British citizen for access by authorities.
"I am delighted that Nick Clegg has stood up for the British public on this," Lib Dem home affairs spokesman Julian Huppert said.
"He is now right to say that what the Home Office propose is unacceptable.
"Spending billions of pounds to keep track of every website we go to, and what we do on Facebook or Google, is simply wrong."
Emma Carr, deputy director of Big Brother Watch, who published a piece on politics.co.uk condemning the snoopers' charter just hours before Clegg made his announcement, said the police already had the power to access online communications if they wanted to.
"Last year Skype gave British police more data than any other government, including the USA," she said.
"To say that the police can’t get data from the internet without this bill is simply wrong. Where security or child safety is at risk, companies already comply with police requests and there was a real risk this bill would make the situation worse by driving dangerous people underground into encrypted services."
Shami Chakrabarti, director of Liberty, said: "If the snoopers' charter really is dead, that's cause for significant celebration and relief.
"People live more and more of their intimate lives online and it was outrageous to suggest surveillance of the entire nation.
"Credit to all those in parliament and beyond with the imagination and courage to block this terrifying plan."
The move will be a shot in the arm to Liberal Democrat activists, who feel it will salvage their battered reputation as defenders of civil liberties.
But Clegg's decision to oppose Theresa May's plans – and especially his decision to announce it on the radio without warning – will worsen already tense coalition relations.
Apparently the deputy prime minister informed the Conservatives on Wednesday he would veto the redrawn proposals from the home secretary.