President Viktor Yushchenko formally called a September election on Tuesday under a deal struck with his rival to end Ukraine's political crisis, but his adversaries cast doubt on the legal grounds for the poll.
Months of turmoil pitting the pro-Western Yushchenko against Prime Minister Viktor Yanukovich, his rival from the 2004 "Orange Revolution", culminated in a hard-won agreement to hold the parliamentary election on September 30.
Parliament last week put in place legislative changes needed for the poll. But Yushchenko's rivals challenged the procedure used to declare the chamber dissolved - the formal resignation of more than 150 opposition members backing the president.
And the assembly, hostile to the president, continued to sit in defiance of his dissolution order. Yushchenko issued a decree naming the date, asking election officials to start preparations and ordering the government to provide finance.
He restated his grounds for dissolution - that more than 150 deputies, one third of the chamber, had quit their seats at weekend party congresses, rendering the assembly unworkable.
Parliament chairman Oleksander Moroz, allied with the prime minister, said procedures and the lists of deputies were flawed. "There are instances of people not having completed the procedure. Others have withdrawn their statements," he told the chamber after a morning of debate on a wide range of issues. "At issue here is a practice unknown in world parliamentary procedure - an assembly being dissolved not on the basis of laws but on the basis of the wishes of specific politicians."
One member of Yanukovich's Regions Party said opposition deputies had gone back on their resignations once they realised that giving up their seats denied them financial benefits.
The two opposition groups, the pro-presidential Our Ukraine Party and the bloc of former prime minister Yulia Tymoshenko, had long lobbied for a new election. They said they followed procedures to the letter.
Yushchenko issued two decrees in April dissolving the chamber and ordering the election, first in May, then in June. Yushchenko took office after defeating Yanukovich in the re-run of a rigged 2004 presidential election following weeks of "orange" protests denouncing poll fraud.
Yanukovich, with his power base in Russian-speaking eastern Ukraine, staged a comeback when his Regions Party came first in a parliamentary poll just a year ago. He was named prime minister when Yushchenko's allies could not form a government.
Months of sniping culminated in Yushchenko's April decrees on grounds that the prime minister was poaching his supporters to boost his parliamentary majority and change the constitution. Recent polls put the two camps backing the president and the prime minister in a virtual dead heat.