The premier's scathing comments on her former ally, Viktor Yushchenko, came a day after the ruling coalition officially split amid political infighting and disagreements over Ukraine's stance on the recent Russia-Georgia conflict.
"Viktor Yushchenko is personally responsible for all negative trends in relations between Russia and Ukraine," Tymoshenko told a news conference in Kiev. Her statement effectively ended any hopes that the coalition will reunite.
The ongoing dispute has seen the presidential Our Ukraine party's popularity plummet, while the Tymoshenko bloc and the pro-Russian opposition Party of Regions have gained ground.
However, Tymoshenko spoke against the idea of early parliamentary elections, saying they would be devastating for the country in light of the ongoing global financial crisis.
Parliamentary Speaker Arseny Yatsenyuk announced collapse of the ruling pro-Western coalition on Tuesday, paving the way for possible early parliamentary polls.
Yushchenko and Tymoshenko were allies in the 2004 "Orange Revolution," but have since drifted apart on a host of issues, including over a recent parliamentary vote to slash the president's powers, and the premier's refusal to back the president's condemnation of the Russian military operation in Georgia.
The legislature now has 30 days to form a new coalition or face an early parliamentary election, the third since Yushchenko came to power. The president has already confirmed his determination to dissolve parliament if the current crisis is not resolved by the deadline.
Tymoshenko is widely expected to run against Yushchenko in presidential elections to be held in 2009 or 2010.