Czech Prime Minister Stanislav Gross has lost his parliamentary majority after a coalition partner voted to quit the government.
Stanislav Gross faces questions about how he paid for a luxury flat
Christian Democrat leader Miroslav Kalousek had urged Mr Gross to resign over a row about his personal finances.
Mr Kalousek said the party would vote against the government in the no-confidence vote called for Friday.
Mr Gross has said he intends to remain in office for as long as his Social Democrat party supports him.
Correspondents say Mr Gross's government could only survive if it wins the support of the Communists, who are due to debate their position on Thursday.
Members of the junior partner in the coalition government met on Wednesday to decide whether or not to stay in government.
The meeting also called on the party's three cabinet ministers to resign from their posts.
The party leader said the Gross scandal had brought the country's political system into disrepute.
"The prime minister has not hesitated to take hostage the trustworthiness of democratic politics with his personal troubles," Mr Kalousek said.
"The Christian Democrats cannot support such actions and cannot take political responsibility for those actions."
The emergency meeting came after Mr Gross's Social Democrats rejected the Christian Democrats' demand for his resignation.
Mr Gross has also refused to step down over the allegations about his family's finances.
The prime minister has faced questions about how he paid for a luxury apartment in Prague five years ago.