Updated

A U.S. law firm hired by the Ukrainian government has concluded that the trial of former prime minister Yulia Tymoshenko was rife with problems including violating her right to defense and unfairly imprisoning her before she was convicted.

However, the report by the New York-based firm Skadden, Arps, Slate, Meagher & Flom — commissioned by the Ukrainian Justice Ministry and released on Thursday — dismissed Tymoshenko's allegations of being prosecuted on political grounds.

Tymoshenko, 51, the country's top opposition leader, is serving a seven-year term on charges of abuse of office, charges condemned by Western nations as politically motivated.

She was convicted of overstepping her authority while negotiating a natural gas deal with Russia in 2009, which the court and the current government deemed harmful for the Ukrainian economy.

Tymoshenko denies all the charges and claims that her opponent, President Viktor Yanukovych, threw her in jail to bar her from politics.

In a 300-page report, the U.S. lawyers concluded that Tymoshenko's three-month arrest on charges of contempt of court before sentencing "raises concerns about whether she was inappropriately deprived of her liberty prior to her conviction."

Tymoshenko's rights to defense were violated when she was left without an attorney for several days and her defense team wasn't allowed to question most of the witnesses they intended to examine, the report said.

However, it concluded that Tymoshenko was not being prosecuted for political reasons.

"Based on our review of the record, we do not believe that Tymoshenko has provided specific evidence of political motivation that would be sufficient to overturn her conviction under American standards," the report read.

The Ukrainian government has said that it paid about 100,000 hryvna (about $12,000) for the report put together over the course of about six months. But Tymoshenko's lawyer dismissed that figure as absurd, saying that a single trip to Ukraine by the U.S. lawyers, of which there were many, must have cost more than that. Serhiy Vlasenko alleged that Skadden was covertly paid well over $1.5 million by a wealthy ally of Yanukovych.

"I am surprised that a big American firm would get involved in such a corrupt story," Vlasenko told The Associated Press.

Agreeing with the report's findings on violations of Tymoshenko's rights, he said: "Let me ask you an indiscreet question: if this is not politically motivated, then why did all those violations take place?"

Skadden would not comment on its fee, citing company policy. Skadden representatives authorized to comment on Vlasenko's allegations could not be immediately reached.

The report was dated September and the reason for the delay in releasing it was unclear. Vlasenko speculated that the government released it at a time when European lawmakers are debating a resolution on Ukraine's ties with the EU and the European Court of Human Rights is getting ready to rule in Tymoshenko's case.

The Justice Ministry declined to comment.