Her distinctive circular braid has been replaced by a loose furl of blond hair, but the unwavering gaze and the stinging rhetoric are those of old.

Seven years since she led Ukraine's orange revolution, Yulia Tymoshenko is back at centre stage as she prepares to stand as the accused in what she calls a show trial orchestrated by President Viktor Yanukovich, her sworn political foe.

"Everything that is happening with me now is ordered and controlled by Yanukovich," she says, as her chauffeur-driven black Mercedes noses through a traffic jam close to Maidan Nezalezhnosti, the square that made her an international celebrity.

"He believes that if he can destroy the opposition in one fell swoop then it will not rise up again. And that's why these criminal cases are being opened against me, one after the other … They are the instrument in Yanukovich's fight against his political opponents, against me – not by democratic, honest and competitive means, but just like Stalin did in 1937."

Tymoshenko's career has soared and dipped since those heady days in 2004 when she and her ally, Viktor Yushchenko, brought hundreds of thousands of Ukrainians on to the Maidan. Back then, she whipped up the crowds against Yanukovich, a former head of the Donetsk coal mining region, who was accused of fixing the country's presidential election in his favour with massive vote-rigging.

It seemed like a victory of democracy over an old Soviet-style regime when the poll was cancelled and Yushchenko won a rerun in early 2005. But he and Tymoshenko, who became his premier, soon fell to bickering and the orange dream began to evaporate.

Last year, Yanukovich made a dramatic comeback – although his hefty support in the Russian-speaking east of the country had never actually dimmed – beating Tymoshenko in presidential elections by just 3.5 percentage points. Soon afterwards, she was ousted as prime minister while Yushchenko faded into political obscurity.

Then, in December, Tymoshenko, 50, was indicted for abuse of power for allegedly using $425m (£266m) of "Kyoto money" received by Ukraine for selling carbon emission quotas while she was prime minister to pay for pensions. Another corruption charge of buying overpriced vehicles for use as rural ambulances soon followed. Finally, last month, she was charged with signing a deal with Russia in 2009 for supplies of natural gas that allegedly lost Ukraine $440m – the case that comes to court .

The accusations have led to a constant merry-go-round of visits by the former businesswoman to the general prosecutor's office, accompanied by television crews and her supporters. For now, she is free, but cannot leave Kiev without prosecutors' consent under strict bail limits. Several of her former government colleagues are already behind bars on charges of fraud, including the former interior minister, Yury Lutsenko.

Tymoshenko rejects the accusations against her as fabricated and claims it is the current government that is corrupt. "Yanukovich is running Ukraine as his own personal company," she says. "His son, a simple dentist, has found his way in to the list of the richest people in the country. How many teeth do you need to pull to do that?" Both men deny any wrongdoing.

Tymoshenko adds: "Yanukovich's ratings are falling fast. He knows that if there is a powerful opposition and honest elections then he will lose power in 2012. He wants to neutralise this threat and make sure that I have no access to the elections."

Her abuse of power charges carry punishments of up to 10 years in jail, but even a suspended sentence could prevent Tymoshenko from taking part in next year's parliamentary poll, and possibly the next presidential election in 2015.

Yanukovich and his allies say they are not involved in the cases. "I wish Yulia Tymoshenko to prove her innocence in court and continue to live, work and do her favourite things," he said last week.

A senior source in the presidential administration said: "The current Ukrainian leadership is trying to be unbiased with regard to law enforcement. No one talks about the 360 [corruption] prosecutions of current members of the government."

But western diplomats say Tymoshenko's trial looks like a politically motivated attack designed to see off an opponent, and part of a wider backsliding on democracy since Yanukovich came to the presidency last year.

That poses a thorny problem as Ukraine wrangles over its future. While often characterised as pro-Moscow , Yanukovich has taken a pragmatic course in foreign policy. He signed off last year on a deal to let Russia keep its Black Sea fleet in Crimea and has ruled out joining Nato, yet his government has also indicated it will sign a free trade agreement with the EU by the end of this year – a snub to the Kremlin's offer of a customs union with Russia, Belarus and Kazakhstan.

EU diplomats insist bringing Ukraine "inside the tent" of economic integration will give greater scope to lean on Yanukovich to improve his human rights record.

But last week a group of Ukrainian intellectuals called on the EU to stall talks on closer ties until Yanukovich halts political trials and "democratic regression". Tymoshenko disagrees. "Ukraine needs to be saved," she said. "If the EU pushes Ukraine away now and leaves it one-on-one with this regime, our country will be thrown back several decades."