MOSCOW – Russia’s most famous party girl has launched a political youth movement that could undermine one of her closest friends: President Putin.

Ksenia Sobchak, 24, is Russia’s most glamorous show-business personality and no stranger to controversy. She has posed nearly nude in a men’s magazine and hosts Russia’s most notorious reality show, a “Big Brother” spin-off.

Until now she has avoided upsetting the Kremlin. Her father, Anatoly Sobchak, the late mayor of St. Petersburg, was Mr. Putin’s mentor and close friend. The only time the Russian president has been seen crying in public was at Sobchak’s funeral in 2000.

So there was surprise last week when Ms. Sobchak appeared to set herself up as a rival to Mr Putin’s administration with the creation of a youth movement called All Are Free. As Russia grows more autocratic, the Kremlin has shown an increasing dislike for youth movements. In 2004, the young led street protests during the Orange Revolution that toppled Ukraine’s pro-Moscow government.

At its launch, Ms. Sobchak was vague about the movement’s intentions, only saying that she planned to teach young Russians “how to be free.”

But in the past two days, she has grown more strident, saying she plans to take on youth movements like Nashi (Ours) and its predecessor Moving Together, created by the Kremlin to counter any attempt to re-create the Orange Revolution.

“All that is happening today makes me awfully sad,” she said.

In theory this kind of challenge should cause consternation in the Kremlin.

But Ms. Sobchak has trouble getting herself taken seriously. As the country’s first “It” girl, she has been compared to an American heiress, Paris Hilton: famous for her family name and for being photographed at all the right parties.

In some ways, Ms. Sobchak has not helped her cause. She was widely quoted as saying she planned to finance the new movement by “pawning her diamonds.”

The world of high society, though, has leapt to her defense, maintaining that her sassiness – an attribute generally lacking in the Kremlin – makes her a threat that should not be discounted.

Nor is she dumb, they say, pointing to her degree in political science and international relations from Moscow State University.

“At first her reputation was tinged with scandal, but in the last two to three years that has changed,” an editor at Russia’s edition of Elle said.

But even if Ms. Sobchak is charismatic and intelligent enough to succeed with her new project, confusion remains about what her ultimate ambitions are.

She claims that her devotion to Mr. Putin has not died. “When my father had been betrayed, Vladimir Putin was the man who helped him and saved him,” Ms. Sobchak said. “I feel enormous gratitude to him.”