Ukraine's highest court has upheld the guilty verdict against Yulia Tymoshenko, former prime minister, who is in jail on abuse of office charges.

Tymoshenko, currently in the hospital, was jailed last October for seven years. Wednesday's ruling, Tymoshenko's last chance at appeal within the nation, confirmed the October sentence.

Tymoshenko was an architect of Ukraine's 2004 Orange Revolution that promoted democracy and a runner-up in the 2010 presidential election.

She was sentenced to seven years in prison in October 2011, when she was found guilty of exceeding her powers while negotiating a gas contract with Russia while she was prime minister.

Her supporters say the trial is politically motivated, initiated by her opponent, the pro-Russian President Viktor Yanukovich, to keep her out of October elections.

The government denies the accusations.

Russian President Vladimir Putin, Tymoshenko's counterpart in signing the gas deal, has said there was nothing illegal in her actions.

The European Union condemned Wednesday's court decision

"We stress the importance for the Ukrainian authorities to take concrete steps to address the systemic problems of the judiciary," Michael Mann, a spokesman for EU foreign policy chief Catherine Ashton, said.

Judge Alexander Elfimov said as he was reading the ruling that the court had "found no grounds to uphold [Tymoshenko's] appeal" of the verdict, and that the prison term is "adequate to the gravity of the crime".

In an official White House statement, Washington called for the release of the former prime minister saying "the charges against Mrs Tymoshenko and the conduct of her trial have raised serious concerns about the government of Ukraine's commitment to democracy and rule of law".

Lawyers for Tymoshenko are appealing the conviction in the European Court for Human Rights.

Tymoshenko's following remains strong in Ukraine, where demonstrations at the prison in support of her are frequent.

At least 500 hundred supporters gathered on Wednesday outside the courthouse in Kiev, chanting "Freedom to Yulia."