They made a striking pair of revolutionaries: Yulia Tymoshenko with her long blonde hair braided in the traditional Ukranian manner, and Viktor Yushchenko, his face addled by a sinister poisoning attempt.

But the heroes of the 2004 Orange revolution have been fighting like Punch and Judy.

The battle between the two leaders of Ukraine took a bizarre turn yesterday when President Yushchenko snatched a government plane that was supposed to be used by Prime Minister Tymoshenko for a crucial trip to Moscow.

The president's version of the incident is that his own plane — due to take him to Lviv in western Ukraine — developed a mechanical fault, forcing him to return to Kiev and take the first available alternative. That just happened to be the Ilyushin-62 earmarked for the Prime minister. Ms Tymoshenko was effectively grounded until a small Cessna could be chartered to do the job.

"The plane has been taken away from the government delegation in order deliberately to thwart the negotiations(in Russia)," said the government press secretary, Maryna Soroka.

The two politicians, nicknamed Beauty and the Beast at the time of the Orange revolution, have since pushed and pulled on almost every major issue facing Ukraine, arguing about privatisation, the powers of president and premier, gas and oil supplies as well as countless official appointments. The government — a coalition between Ms Tymoshenko's party and that of Mr Yushchenko — has foundered and the insults have been flying thick and fast.

A key source of conflict is over the relationship to Moscow.

When Ms Tymoshenko eventually got to Moscow yesterday the talks with Vladimir Putin, the Russian prime minister, centred on a four year supply contract for Russian gas, to begin next year.Ms Tymoshenko, according to the newspaper Kommersant Ukraine, is aiming for a direct relationship between Naftogaz, the Ukrainian national oil and gas concern, and Russian Gazprom. The deal, if clinched, would allow Naftogaz to re-export the gas to the European Union jointly with Gazprom. But Russia is also pressing for the gas to be set at market rather than contractual prices and for a quick repayment of Ukraine's dollars 1.8 billion debt to Gazprom for gas supplied in 2008.

Since Russia has in the past used gas supply as an instrument of policy against neighbouring states, the talks are being watched closely by the whole of the Ukrainian political class. The key question is whether Ms Tymoshenko will give too much ground to the Kremlin. President and Prime Minister are at loggerheads over Mr Yushchenko's openly critical view of Moscow's intervention in Georgia. In August he told the Times that the war was a compelling reason for accepting Ukrainian membership of Nato. Ms Tymoshenko on the other hand has voiced almost no criticism of the Kremlin about the Georgian crisis.

This prompted accusations from presidential advisers that Ms Tymoshenko was soft-peddling on Russia in order to win Russian cash and government support for her bid to supplant Mr Yushchenko as president. Elections have to be held before 2010 and jostling for position has already begun. The Secret Service has been asked to investigate whether the prime minister had acted "to damage the country's national interests." Last month the President said Ms Tymoshenko's actions were "aimed at destabilising the situation" and were tantamount to treason.

The Prime Minister in turn questioned the state of the President's mental health. And in a particularly low blow she mocked the nearly fatal dioxin poisoning attempt on Mr Yushchenko. The attempt, still not fully explained, has left his face badly disfigured.

"The main poisoning is the poison of unlimited power, a serious intoxication in the presidential secretariat," she said.

Times Recommends

• Rio Tinto four held as China prepares case
• Diplomats must keep heads down and trousers up
• When in Rome should one make like Berlusconi?