Poland's Law and Justice (PiS) conservatives on Tuesday confirmed party vice-president Beata Szydlo as their candidate for prime minister, after the party won a landslide victory in the weekend's general election.

"Beata Szydlo is the candidate to become prime minister," the PAP press agency reported PiS spokeswoman Elzbieta Wilk as saying, adding that she was making the declaration to "cut short" speculation about the party's choice for the role.

Media reports had touted powerful PiS chief Jaroslaw Kaczynski as a possible nominee after the party won took an outright majority in the lower house on Sunday, boosted by anti-refugee rhetoric and welfare promises.

Others had named economist Piotr Glinki, who has been a candidate for the post in the past.

Kaczynski proposed Szydlo as a candidate to head any PiS government last June, after the coalminer's daughter ran a victorious presidential campaign for political greenhorn Andrzej Duda.  

As an MP, she has defended conservative positions on issues such as abortion, in-vitro fertilisation and the 2011 Istanbul Convention -- the world's first legally-binding instrument to prevent and combat violence against women.

Her promises target the core conservative electorate in the poorer, devoutly Catholic east and public sector workers.

Kaczynski is the undisputed leader of PiS, which he co-founded with his identical twin brother Lech. He served as prime minister in 2006-7 while Lech was president, before his sibling died in a plane crash in western Russia in 2010.

The PiS now controls both the presidency and the lower house -- ousting leftist parties from parliament for the first time since the fall of communism in 1989 -- after it won 235 seats out of 460 in Sunday's polls.

Prime Minister Ewa Kopacz's centrist Civic Platform party won only 138 seats, leaving it in opposition after eight years in power.