“You should not be in jail,” European Parliament President Jerzy Buzek wrote on Yulia Tymoshenko’s Facebook wall on Sunday as Ukraine’s ex-prime minister marked her 51st birthday.
Hundreds of Tymoshenko supporters have been rallying outside her prison in the capital Kiev, but there were no clashes with police.
There were also fireworks and live music.
“There is unfortunately nothing to celebrate,” Buzek said in a statement. “Particularly when we receive information on the deterioration of her state of health and the lack of appropriate medical treatment.
Tymoshenko was taken to hospital earlier this week after concern over her health but was brought back to prison within hours.
The former prime minister was jailed last month for seven years for acting beyond her powers in sealing a gas deal with Russia in 2009.
The European Union and United States described the trial as politically motivated, and Russia said the jailing had a “clear anti-Russian subtext.”
Buzek said authorities should ensure Tymoshenko receives “all the necessary medical treatment.”
“The right to medical treatment is a basic right of prisoners and the lack of this treatment in Tymoshenko case is very harmful for the credibility of Ukrainian authorities,” he said.
“I also propose that Ukrainian authorities let independent, international doctors - with Tymoshenko’s permission - to proceed with a health check and to suggest appropriate treatment.”
Buzek said new charges leveled at Tymoshenko earlier this month “shed light on the lack of independence of the Ukrainian judiciary and on the partisanship of Ukraine's elite.”
Prosecutors accused Tymoshenko of concealing foreign currency revenues and evading taxes while serving head of United Energy Systems of Ukraine in the mid-1990s.
“Ukraine cannot be welcome in the European family if Ukrainian authorities do not respect European standards and values,” Buzek warned.