Yulia Tymoshenko, Ukraine’s prime minister, has called for an investigation into President Viktor Yushchenko’s inner circle after accusing individuals of profiting from bets against the currency last week as the country struggled to avoid financial meltdown.

The prime minister demanded the resignation of Mr Yushchenko, and named Dmytro Firtash, the billionaire and Gazprom partner in the supply of natural gas to Ukraine and Europe, as a co-conspirator in the alleged currency speculation.