Former EU chief Donald Tusk was poised to announce his candidacy to lead Poland's opposition Civic Platform party on Saturday, signalling a return to the political frontline.

The 64-year-old co-founded Civic Platform (PO) two decades ago and served as prime minister of Poland between 2007 and 2014.

He is currently chairman of the centre-right European People's Party and a frequent acerbic commentator from the sidelines of Polish politics.

"Donald Tusk will return," Tomasz Siemoniak, the party's deputy chairman, said on Friday on the eve of the party congress.

Malgorzata Kidawa-Blonska, another party MP and the deputy speaker of parliament, said Tusk's return would "solve many of our problems" and was "the way we are all waiting for".

A self-avowed football hooligan in his youth, Tusk grew up in the northern port city of Gdansk which was the cradle of the Solidarity movement that dismantled Communist rule.

During his time as president of the European Council from 2014-2019 he handled crises ranging from migration to Greece's economic plight to tough Brexit negotiations.

There was uncertainty in the run-up to the party congress after Warsaw mayor Rafal Trzaskowski, the runner-up in a presidential election last year, said he wanted to head the party.

According to media reports, Trzaskowski will no longer challenge Tusk for the leadership.

The party has lagged third in the polls behind the ruling Law and Justice (PiS) party and the opposition Poland 2050 party.

At the same time, the PiS has lost its narrow majority in parliament and relations with the EU are plunging on a number of issues, including controversial judicial reforms.

Tusk listens to then-Maltese Prime Minister Joseph Muscat at an EU Council summit in October 2017. Photo: AFP

An early election?

Elections in Poland are currently scheduled for 2023 but commentators say the governing party could be tempted by early elections to avoid a no-confidence vote in parliament.

The PiS is also holding its own leadership congress on Saturday at which the party is widely expected to confirm 72-year-old powerbroker Jaroslaw Kaczynski as its leader.

The party is set to approve 53-year-old Prime Minister Mateusz Morawiecki as deputy leader, making him in effect Kaczynski's heir apparent.

A new poll earlier this week showed the governing right-wing coalition dominated by the PiS in the lead with 34 per cent, followed by Poland 2050 on 17.1 per cent.

The survey was carried out by the IBRiS polling company for TV channel Polsat.