Britain spied on Russia with a fake rock loaded with hi-tech surveillance equipment in the middle of Moscow, a former senior government official has admitted.
Russia released footage in 2006 it claimed showed the fake rock and British agents visiting it but the film was dismissed as a Moscow propaganda stunt.
But Jonathan Powell, former prime minister Tony Blair's chief of staff, has admitted that the UK was guilty of spying.
"The spy rock was embarrassing. They had us bang to rights. Clearly they had known about it for some time and had been saving it up for a political purpose," Powell told BBC2 documentary Putin, Russia and the West, which airs on 19 January.
Blair tried to brush off the claims at a 2006 news conference.
"I'm afraid you're going to get the old stock-in-trade, of never commenting on security matters," he said. "Except when we want to, obviously."
Russia's secret service accused British diplomats of using the rock to make covert payments to non-governmental organisations (NGOs) promoting human rights and democracy.
Vladimir Putin, Russia's president, used the footage to bring in laws against NGOs, making it illegal for them to receive money from foreign governments and causing many to close down.
"We have seen attempts by the secret services to make use of NGOs. NGOs have been financed through secret service channels. No-one can deny that this money stinks," said Putin.