A former British official has acknowledged that London spied on Moscow with a fake rock that contained electronic equipment, confirming Russian intelligence claims from 2006 that were mocked but gave Vladimir Putin justification to crack down on nongovernmental organizations.

Thursday's revelation could prove timely to the prime minister in his latest campaign against independent NGOs, which he has accused of using foreign money to destabilize the country during State Duma elections last month and before a presidential vote in March.

Jonathan Powell, chief of staff for Prime Minister Tony Blair during his decade in office, told a BBC documentary that the Federal Security Service "had us bang to rights" when it announced in January 2006 that it had caught British spies collecting information from Russian nationals via a fake rock planted in a Moscow park.

"There's not much you can say. You can't really call up and say, 'I'm terribly sorry about that, it won't happen again,'" Powell said on "Putin, Russia and the West," which was aired on BBC Two late Thursday.

The FSB announced in 2006 that it had uncovered four British diplomats from the Moscow embassy planting the hollow rock and retrieving information from it with pocket computers. It said the information had been transmitted for storage in the rock by two Russian nationals, who were both in custody.

One of the accused British diplomats, Marc Doe, authorized grants for 12 Russian NGOs, including the Moscow Helsinki Group and the New Eurasia Foundation, as the second secretary of the embassy's political section.

Powell hinted at a link between the FSB exposing British agents and Putin's crackdown on NGOs.

"Clearly they'd known about it for some time and were saving it up for a political purpose," he said.

Oddly, Putin refused to expel the Britons, even though the practice is customary in such situations, and the FSB had initially indicated that the diplomats would be sent home.

"If we send them away, more will come," Putin said, speaking two weeks after signing a tough NGO law criticized by Russian NGOs and the West. "Maybe clever ones will come. And we will have to struggle to find them."

Putin added: "It has now become clear to many why Russia passed a law regulating NGO activities."

The British government, which made no public comment on Powell's remarks Thursday, has denied improperly funding Russian NGOs.

The fake rock claims were questioned by NGOs and several prominent journalists at the time, and reporter Arkady Mamontov, who broke the story on Rossia state television, said Thursday that television journalist Leonid Parfyonov and Moscow Helsinki Group head Lyudmila Alexeyeva had "made fun of me." But Mamontov, in an interview on Izvestia's web site, said he now felt vindicated.

The Moscow Helsinki Group unsuccessfully filed libel lawsuits against Rossia and other channels that broadcast the fake rock report.

What happened to the Russian nationals arrested in connection with the fake rock remains unclear. No information about any trial has been reported.

Andrei Soldatov, a security services analyst with Agentura.ru, a think tank, said he believed that the FSB had abandoned the case against the Russian nationals to search — unsuccessfully — for a link between the Russian NGOs and the British diplomats' spying activities.

It was unclear why Powell decided to speak out now, but Soldatov said his words might be used against opposition-minded activists who meet with foreign officials. He cited as an example this week's meeting of opposition and NGO activists with new U.S. Ambassador Michael McFaul. "This is another embassy, but who cares?" Soldatov said.

He was echoed by veteran human rights champion Lev Ponomaryov, who said that Putin could use the situation to his advantage as he runs for a third term as president in the March election. "He could talk about his foreign and domestic enemies at the same time. This is a typical KGB trick," he said.

During his call-in show last month, Putin accused NGOs of playing a role in the organization of tens of thousands of protesters who hit the streets to challenge the Duma elections.

But Stanislav Belkovsky, an independent political analyst, said he doubted that the latest developments would have much influence on domestic politics. "Society has become less sensitive to spy allegations, and it has even gotten to the point that they can be used to the advantage of those accused of spying," he said.