A feud over a hulking steel plant controlled by one of Ukraine's leading tycoons was the tripwire for the implosion that last week destroyed the coalition that led Ukraine's Orange Revolution last year.

The breakup has become more bitter by the day as the alliance's dominant figures, President Viktor Yushchenko and former prime minister Yulia Tymoshenko, trade accusations about billion-dollar graft concerning the plant.

The unlikely third party in this political divorce is Viktor Pinchuk, who grew wealthy under the corrupt structure that Yushchenko and Tymoshenko, acting together, ostensibly toppled.

Each side professes its innocence and shouts its dismay. But the persistence of massive corruption, whoever is behind it, is now a strikingly public issue, a departure from the refusal of the old government headed by President Leonid Kuchma to discuss the issue openly.

In separate discussions with journalists this week, Yushchenko and Tymoshenko voiced rare agreement on one point: that this may be a defining moment in moving the country toward the justice and openness that each promised the hundreds of thousands of citizens who turned out onto the streets and helped sweep them into power.

"It's painful to speak about these things because, first of all, I'm speaking about a lady," Yushchenko said in a 90-minute discussion with foreign journalists. "I'm just happy I managed to eliminate double standards."

"The air we are breathing is corrupt," Tymoshenko said in an interview. "It's not the end of the Orange Revolution; it's the direct action of the Orange Revolution. A public cleansing of society is underway."

The dispute focuses on the Nikopol Ferroalloy Plant, one of the world's leading suppliers of high-quality mixtures of metals. In 2003, Pinchuk, the billionaire son-in-law of Kuchma, acquired a majority stake in the state-owned facility for $80 million. There were accusations at the time that the sale was rigged and that the factory was worth vastly more -- over $1 billion, according to Tymoshenko.

In an interview, Pinchuk said the auction was open. He noted that the price he paid was the highest ever for a piece of state property in Ukraine.

Earlier this year, after Kuchma left office, one of Pinchuk's business rivals, the Pryvatbank group, challenged the privatization in court. Here the allegations and counter-allegations begin, and they also involve prominent television stations.

According to Yushchenko, the prime minister directly pressured the courts on behalf of Pryvatbank to overturn the privatization and return the plant to the state. "You can ask the judges how much pressure they received," he said.

"The plot . . . involved discussion of the ownership of one of the major Ukrainian TV channels and in order to bring about this, the prime minister acted in such a manner," Yushchenko said.

According to some of Yushchenko's closest supporters, the Pryvatbank group was also seeking to buy the 1+1 television channel and promised to throw the network's editorial weight behind Tymoshenko in next March's parliamentary elections if she wrested the Nikopol plant from Pinchuk and ensured Pryvatbank got it.

The courts eventually ruled that Pinchuk had to surrender his shares.

Tymoshenko flatly denies any such intervention. She said in an interview that Pryvatbank's challenge to the original privatization was simply an attempt to undo an auction that the company viewed as tainted and to bring about a new one in which Pryvatbank could compete fairly.

The state, she said, joined as a third party as a matter of law and planned to hold an open auction for the property after the courts overturned the original sale. She said it was the presidential administration that attempted to interfere with the legal process, not her.

"The judges were pressured by the president's lieutenants to leave the plant in Kuchma's family," Tymoshenko said. "The judges didn't go for that."

The prime minister, who was dismissed along with her cabinet last week by Yushchenko, went on in the interview to argue that one of Yushchenko's key advisers, Petro Poroshenko, was trying to keep the plant in Pinchuk's hands in return for Pinchuk selling his TV stations, ICTV and the New Channel, to people who would use them to support the president's camp in the parliamentary elections.

"They agreed to leave the plant with Pinchuk in exchange for TV channels," Tymoshenko said. The channels remain in Pinchuk's hands.

In an interview, Poroshenko denied there was any such deal. He said that he met Pinchuk in either June or July and that the businessman asked only that he receive equal treatment before the law.

"I prefer not to comment," Pinchuk said when asked about an alleged deal with Poroshenko over the television channels.

The coalition began to come apart last week when Oleksandr Zinchenko, head of the presidential secretariat and a key organizer of the Orange Revolution, resigned, charging that the president was threatened by corruption within his closest circle. Poroshenko quit in response to his accusations but denied wrongdoing.

Yushchenko said Zinchenko has yet to present a single piece of evidence supporting his allegations. And he quickly turned on the prime minister, contending that she was the cause of much of the corruption.

He accused Tymoshenko of a separate case of corruption -- using her office to wipe out debts of more than $1 billion accumulated by an energy company she formerly owned. Tymoshenko dismissed the allegation as an attempt to distract attention from what she said was rampant corruption among the president's closest confidants.

"Entrepreneurs are being forced to pay money so their property stays with them," Tymoshenko said. "People are asked to pay dividends for political support. People were forced to give up buildings in downtown Kiev."

President Viktor Yushchenko and his former prime minister have traded accusations of improprieties.Yulia Tymoshenko, a partner of Yushchenko's in the Orange Revolution, was ousted last week. Viktor Pinchuk, a tycoon with family ties to the previous president, is a central figure in the allegations.