Romania's prime minister Mihai Tudose | AFP via Getty Images Romanian PM resigns Mihai Tudose becomes second PM in a year to be forced out.

Romania was thrown into fresh political crisis Monday as the second prime minister in a year said he would resign "tonight or tomorrow morning" after losing his Social Democrat party's support.

Mihai Tudose's resignation comes amid growing tensions with PSD leader Liviu Dragnea, who cannot be prime minister because of a suspended jail sentence he received for rigging a referendum.

Tudose took over in June 2017, after his predecessor Sorin Grindeanu was ousted by the PSD and its junior coalition partner ALDE, who argued that Grindeanu had fallen behind schedule implementing a reform program.

"The party decided that there is a need for a new government, with a new approach," Tudose told reporters after leaving a party leadership meeting on Monday evening in Bucharest. The deputy prime minister, Paul Stănescu, will become interim prime minister on Tuesday, he said.

PSD will hold a leadership meeting on Tuesday morning to come up with a new nomination for leader, Dragnea said, adding that he wouldn't make the choice himself.

Asked about the reasons behind Tudose losing support, Dragnea said "there was a conflict between the party and the government, and inside the government as well."

In recent weeks the prime minister had clashed with the interior minister, Carmen Dan, a close ally of Dragnea. Dan wanted Tudose to sack the head of the Romanian police over the case of a policeman accused of pedophilia. Tudose refused to do so and suggested that Dan resign.

PSD and ALDE will now have to nominate a new prime minister, with the choice needing the approval of Romanian President Klaus Iohannis. It will be third time he will have had to approve a prime minister since December 2016 elections.

PSD won some 46 percent in those elections on promises of tax cuts and increased wages and pensions. A year on, many of those promises have not been realized, and a decision to shift the burden of social security contributions onto employees caused mass protests last year.

Last year the country was rocked by the biggest protests since the fall of communism when people took to the streets to protest against an emergency decree that would have decriminalized some acts of corruption. The government eventually withdrew the decree, but the parliament last year passed other changes to judiciary laws that opponents feel may impact the justice system's work on corruption.