Rivals of Ukraine's Viktor Yushchenko voted in parliament today to curb the president's powers in a potentially mortal blow to his authority.
Deputies supporting Mr Yushchenko's foe Prime Minister Viktor Yanukovich and his former ally-turned-rival Yulia Tymoshenko won two thirds of the votes in the 450-seat parliament to overturn the president's veto.
Under a new law Mr Yushchenko loses the power to veto parliament's choice of prime minister and pick the defence and foreign ministers, two of his few allies in the current government.
Mr Yushchenko, who took over after the 2004 Orange Revolution, also had limits placed on presidential decrees.
His 'Our Ukraine' party stormed out of parliament after the vote, calling it "anti-constitutional and aimed at monopolising the power of the prime minister".
"We are speaking here about a factual destabilisation of the state power in Ukraine," Arseniy Yatsenyuk, first deputy to the presidential secretariat, told reporters. "A principle of dividing the powers has been violated."
He said Mr Yushchenko planned to challenge the vote in the Constitutional Court, even though the constitution states he has to sign it into law.
Mr Yanukovich said the new law would allow government to work more effectively.
"We will use the powers to solve many problematic questions in the country. For the first time in 15 years the government got an opportunity to work and have powers," he was quoted as saying by Ukrainska Pravda website, www.pravda.com.ua.
Mr Yushchenko defeated Mr Yanukovich in the presidential election after the Orange Revolution but was forced to appoint him as prime minister in August after his own allies failed to form a government.
Since taking power Mr Yanukovich has secured control over key economic sectors.
Mr Yushchenko's powers were reduced after a constitutional reform passed in the midst of mass street protests in 2004 that handed parliament the power to pick the prime minister.
Earlier this week parliament voted to ban farm land sales for another year, a reform Mr Yushchenko had considered crucial. Now analysts say the president could be fatally wounded.
"Yushchenko appears to have been holed below the water line. The question is will he simply grin and bear it, or will he seek to undertake a rear guard action?" Tim Ash, an economist at Bear Stearns in London, said in a research note.
"Yushchenko could still make life difficult for the government."
Parliament passed the law for the first time in December but Mr Yushchenko vetoed it. Under the constitution he now must sign it into the law.