BUCHAREST, June 15 -- Romania's major ruling Social Democratic Party decided Thursday to submit a censure motion against its own government to topple Prime Minister Sorin Grindeanu who refuses to resign.

The Social Democrat leadership made the move at a meeting of the National Executive Committee by unanimous votes.

The Executive Committee also voted, unanimously, to expel Grindeanu from the party.

Party leader Liviu Dragnea announced late Wednesday to call the meeting to nominate a new prime minister after the party decided to withdraw its political support for Grindeanu.

Grindeanu has a tense relationship with the party's main leaders recently and refused to take the initiative to resign.

Grindeanu reiterated his position of not resigning even after extreme measures taken by his party against him.

Under the Constitution, the only feasible means to make the prime minister to step down is a vote of no confidence in the parliament.

Yet, the Thursday move of the Social Democrats set a historical precedent in the country that the parliament majority impeaches its own government.