The Lista Marjana Šarca (LMS) under Marjan Šarec, mayor of the city of Kamnik, drew the support of 15.7 percent with a junior governing coalition party, the Social Democrats, in second place with 12.6 percent and the leading opposition party, the centre-left Slovenian Democratic Party, with 12.2 percent.

The Party of Modern Centre led by Prime Minister Miro Cerar came in sixth with 5.5 percent. Last month, the Social Democrats led the same poll with 19.8 percent while the LMS was not yet included in the survey.

Šarec surprised many last month when he was narrowly beaten in a presidential run-off election, gathering about 47 percent to incumbent Borut Pahor's 53 percent.

Analysts said Šarec's party, which has so far been active only at local level, could win a parliamentary vote amid general dissatisfaction with the centre-left government, above all its inability to improve the inefficient national health system.

The government of the southeast European country is also under heavy pressure from various public sector unions demanding wage hikes at a time of strong economic growth, expected to be 4.4 percent this year, up from 3.1 percent in 2016.

Pahor will call a general election in the coming months and it is expected to be held in the first half of June.