Tymoshenko - a West-leaning former prime minister who has vowed a radical opposition to the recently installed coalition government - Iosif Vinskiy and Halyna Harmash signed Friday a declaration on the parliamentary opposition.
"It is a landmark event because parliament will for the first time in the years of independence have an opposition with a clear lineup and a precise idea of what it is doing," Tymoshenko told reporters before signing the document.
The ex-premier, who served for about eight months under President Viktor Yushchenko in 2005, said the opposition would work to prevent those in power from arbitrary and irresponsible actions. She has been a vocal critic of Prime Minister Viktor Yanukovych both when he was in opposition to her government and during his first stint as prime minister under Leonid Kuchma between 2002 and 2004.
Tymoshenko has said she expected another West-leaning bloc, pro-presidential Our Ukraine, to join the opposition but it has shown little interest in the offer yet. Our Ukraine is currently in talks with the ruling coalition of the Party of Regions, the Socialists and Communists over forming a broad coalition of national unity.
Last week, Tymoshenko said she would summon all opposition forces in the country for a unifying forum in October.
The Yulia Tymoshenko Bloc, which won 129 seats in the 450-member Supreme Rada at the March 26 elections, was the leading force in the first parliamentary coalition to emerge after the elections. But the alliance collapsed when the Socialists defected to join the Party of Regions, led by President Viktor Yushchenko's former rival in the 2004 election, Viktor Yanukovych.
Three members of Tymoshenko's parliamentary faction have since left and joined the coalition.
