Former Ukrainian Prime Minister Yulia Tymoshenko on Monday said the authorities had told her they planned to discharge her from hospital and send her back to prison, a move she said amounted to "another act of revenge".
But the state prison service, which said last week it planned to ask the former premier's doctors whether she needed further treatment, denied it had handed her any such notification.
Opposition leader Tymoshenko, 51, was sentenced to seven years in jail last year after being found guilty of abusing her authority when prime minister in a case the West condemned as an example of politically-motivated selective justice.
But in May she was moved from her prison in the city of Kharkiv to a local state-run hospital for treatment for back trouble.
If she is sent back to prison ahead of an Oct. 28 parliamentary election, opposition parties hoping to defeat President Viktor Yanukovich's Party of the Regions, would be likely to try to make political capital out of it.
Yanukovich's party currently has a majority in parliament.
"The prison service has handed me a paper giving me notice that (my) treatment is being stopped and that I will be discharged in yet another act of revenge," Tymoshenko said in a statement published by her party Batkivshchyna (Fatherland).
The state prison service denied that in its own statement, saying that such documents did not exist.
In an emotional video appeal filmed in hospital last week, Tymoshenko called on Ukrainians to "rise up" during the parliamentary election to end Yanukovich's "criminal rule".
She is accused of tax evasion and embezzlement in a separate trial which has been delayed for months because of her treatment. She denies any wrongdoing, saying her prosecution has been ordered by Yanukovich.
Shortly after her conviction last year, the European Union shelved a landmark agreement on political association and free trade it was planning to sign with Ukraine. Last month, EU and U.S. officials said Tymoshenko's continued imprisonment could affect how they assess the upcoming election.
Tymoshenko helped lead the 2004 "Orange Revolution" protests which derailed Yanukovich's first bid for the presidency and went on to serve twice as prime minister before losing the 2010 presidential vote to Yanukovich in a close run-off.