LONDON (Reuters) - Socialite-turned-Kremlin-critic Ksenia Sobchak told Russian dissidents in London on Monday that growing repression at home would prompt more and more people to fight for change but warned that a full-blown revolution could destroy her country.

Once an apolitical tabloid celebrity and a Playboy cover girl, Sobchak has emerged as an unlikely but fierce critic of President Vladimir Putin in the past year, taking on a man who was once a close political ally and friend of her late father.

Addressing an audience of activists, academics and ordinary Russians, Sobchak urged fellow opposition politicians to undermine Putin's rule by poaching potential dissidents from within the system, and campaigning for free and fair elections.

"We are living in a very dynamically changing situation. A lot of the people who have fallen out of love with Putin are not going to fall in love with him again," Sobchak, 31, said.

"(But) in a revolutionary scenario it would be the people who would ultimately lose ... In a revolutionary scenario we would all lose, not just Putin."

Since returning to the Kremlin for a six-year third term, Putin and his administration have enacted a raft of laws that critics say are aimed at cracking down on dissent, a process Sobchak said was fuelling public anger.

The daughter of late St. Petersburg Mayor Anatoly Sobchak for whom Putin worked as a deputy in the 1990s, she was once dubbed "Russia's Paris Hilton" and is a household name in her native Russia for hosting a TV reality show.

However, state TV channels shunned her after she joined the opposition, prompting one U.S. newspaper to describe her as a "stiletto in Putin's side".

Her apartment was raided by police ahead of a June protest against Putin and she is now one of the faces of the movement, though her views are seen as moderate compared to other figures and some in the opposition question her credibility.

"The protest in Russia is not just a political protest, it's a generational protest," said Sobchak, dressed demurely in a simple black and green dress. "And despite the tough period that lies ahead, this is an inevitable process towards success."

Russia's opposition movement, which drew tens of thousands of demonstrators in Moscow in the months following the December 4 parliamentary and March 4 presidential elections, has dwindled in recent months, failing to galvanize activists.

The Kremlin denies it is clamping down on the opposition for political reasons but has accused foreign governments, including the United States, of meddling in Russia's domestic affairs.

(Reporting by Maria Golovnina; Editing by Andrew Osborn)