"The situation in Ukraine is now very volatile. It is urgent that they establish a new government and even more urgent that they speed up the reform process," Secretary General of the Council of Europe Thorbjorn Jagland said on Monday, according to Press TV.
"A new government will have to take this on in a much more impressive way than has been the case until now."
Yatsenyuk has faced repeated accusations of corruption since coming to power in 2014. He narrowly survived a vote of no-confidence in February.
During his resignation speech, Yatsenyuk warned that destabilization in Ukraine is "inevitable" without the quick formulation of a new government.
"We cannot allow one thing [to happen] – the destabilization of the executive power during the war [in the southeastern region of Donbass]. This prospect is inevitable, if after the resignation, a new government is not formed," he said.
"Since now, I see my goals broader than the powers of the government head."
Yatsenyuk’s government was beset by problems from the start. Kiev faces a deep economic crisis, as well as conflict in the country’s east.
Ukrainian President Petro Poroshenko recently nominated Chairman of the Verkhovna Rada Volodymir Groisman as the nation’s new prime minister.
Last month, chairman of the Entrepreneurs Council at the Cabinet of Ministers and Chairman of the Ukrainian Agrarian Confederation Leonid Kozachenko also resigned, citing the Yatsenyuk government’s failure to pursue promised reforms.
"Summarizing the results of one and a half years of work, there’s a serious threat not just to the country’s economy, but to the mere existence of the state," he said.
