Russia's central election commission has disqualified the sole liberal challenger to Vladimir Putin from the March 4 presidential ballot, in a move slammed by the opposition as undermining the legitimacy of the polls.
The commission said on Friday it could not accept about a quarter of the registration signatures gathered by Grigory Yavlinsky, founder of the Yabloko (Apple) party, because they were either photocopies of originals or fakes.
"I am sad to announce that we will not able to register Yavlinsky as a candidate," Sergei Danilenko, election commission member, told a special hearing.
Russia's presidential election rules have grown progressively stricter since 1996 and now require all independent candidates to collect two million signatures to win registration.
The restriction has been heavily criticised by the candidates as well as the growing protest movement against Putin, who will be standing for a third Kremlin term in the polls after his four-year stint as prime minister.
The PARNAS opposition group of former liberal cabinet members called on Putin to delay the election because of the decision, while Yavlinsky vowed to challenge the move in court.
"We are preparing an appeal," Yavlinky told reporters. "I am certain that Putin is the person who issued the instruction" for the election authorities to act.
The decision has the potential of adding still more momentum to a spreading opposition movement that plans to stage a third in a series of rallies in Moscow and other big cities against Putin on February 4.
Putin's spokesman moved quickly to stamp out charges from Yabloko that the expulsion laid to waste the Kremlin's claims of planning to hold a fair vote.
"If one of the candidates fails to collect the required number of signatures, this does not mean you can make claims about the vote's illegitimacy," Dmitry Peskov told the RIA Novosti state news agency.
Putin had doubled the number of signatures required for candidates' registration in 2004, a year in which he stepped up his campaign to centralise power by also announcing an end to direct elections for regional governors.
The presidential election rules were tightened again in 2007 when Putin was about to hand power to his hand-picked successor Dmitry Medvedev, giving candidates just a month to rally their support instead of the previous three.
Facing Russia's largest protests since the turbulent 1990s, Medvedev last month proposed reducing the required signatures number, a move the opposition said was being made too late.
The vote is now set to feature Putin and three leaders of nominally opposition parties who all lost presidential elections before, as well as the billionaire tycoon Mikhail Prokhorov.
A precious metals magnate who owns the New Jersey Nets basketball team in the NBA, Prokhorov also heavily criticised officials for threatening Yavlinsky with expulsion this week, calling current election rules unfair.
Yavlinsky, who was shown winning less than three per cent of the vote in most polls, founded Yabloko in 1993 as Russia struggled with a post-Soviet economic crisis that left many impoverished and looking for social protection.
The 59-year-old economist always promoted more socially oriented policies and twice ran for president, failing to break the 10-per cent barrier in both 1996 and 2000.