(Adds timing of vote, quotes from Social Democrat, rebel MPs)
By Jan Korselt
PRAGUE, March 17 (Reuters) - The main Czech opposition party called a no-confidence vote for next Tuesday in a new attempt to dislodge Prime Minister Mirek Topolanek halfway through the central European country's EU presidency.
The leftist Social Democrats have failed several times in the past to topple the centre-right cabinet, but his position has become more shaky due to a string of defections.
The grounds for the latest no-confidence vote are reported attempts by a Topolanek aide to influence the media. The opposition has also criticised government measures to combat the economic crisis.
"Social Democrats reject corruption, Mafia-style practices, unpopular reforms including a reform of healthcare, incompetence in resolving the economic crisis and inability to assemble a realistic budget this year," Social Democrat leader Jiri Paroubek said.
The Czech Republic has avoided a financial meltdown due to the global crisis and its currency has recovered from losses seen earlier this year, but the central European economy has been badly hit by a collapse in demand for its exports.
Neither the three government parties nor the opposition command a majority in the 200-member lower house. The government has 96 votes and the opposition 97, the rest being unaffiliated defectors from both government and opposition camps.
The opposition needs 101 votes to win the no-confidence motion, a majority it has failed to find in four attempts to overthrow the cabinet since 2007.
The government has often suffered partial defeats in the lower house, but independent deputies have helped keep it afloat in key votes so far.
EU PRESIDENCY
A loss in a no-confidence vote would trigger the resignation of the cabinet but would not directly lead to a new election.
Under the Czech constitution, the cabinet would stay in power with an unrestricted mandate until a new administration is formed, which could take weeks or even months.
"This government could stay in power until the end of the EU presidency (in June), without taking any irreversible steps. And the president would have enough time to consider who he would delegate to put together the new government," Social Democrat Vice-Chairman Bohuslav Sobotka said.
He said there could be an agreement on early election.
Analysts said the swelling ranks of rebellious deputies from the government coalition posed a bigger threat to the cabinet than before, which made the vote result less easy to predict.
"The chance that the opposition succeeds is maybe higher now than in the previous attempts," said Petr Just, political analyst at Charles University.
"The difference is the situation of two former deputies of the Green party who have not only left the party's caucus but have also been expelled from the party."
The two deputies told Reuters they were not decided how to vote. One rebellious member of the ruling Civic Democrats, Juraj Raninec, said he may vote against the government if there is an alternative plan.
The Civic Democrats have ruled in coalition with the centrist Christian Democrats and the Green Party since January 2007. (Additional reporting by Jana Mlcochocva, writing by Jan Lopatka; Editing by Charles Dick)