Poland's liberal opposition on Sunday urged voters to boycott the 10 May presidential election, which the right-wing government has controversially refused to postpone despite the risks posed by the COVID-19 pandemic.

The right-wing Law and Justice (PiS) government came under heavy pressure this week over its decision to continue with the election, as an opinion poll showed that 72% of respondents wanted the ballot postponed. 

Surveys also show a surge in the popularity of PiS-allied incumbent President Andrzej Duda amid the crisis, giving him a shot at a first-round victory.

"Let's boycott these elections, your lives are the most important," Malgorzata Kidawa-Blonska, Duda's main liberal rival, told reporters in Warsaw on Sunday, adding that she would suspend her campaign to focus on fighting the pandemic.

She also issued a separate statement insisting that "organising presidential elections could even be criminal" under the current conditions.

President Andrzej Duda speaks during presidential election convention in Nysa

"How can you ask for people's trust and at the same time persuade them to risk their lives?" she asked.

Prime Minister Mateusz Morawiecki and powerful PiS leader Jaroslaw Kaczynski, a close Duda ally, have said they see no reason to postpone the election.

Duda himself admitted on Saturday that the current "election date may turn out to be unsustainable" should the pandemic "still be raging" in mid-May. 

Poland's PiS-dominated parliament on Saturday adopted rules allowing people over 60, in quarantine or self-isolation to vote via postal ballot, a move the opposition slammed as being unconstitutional.

While the Senate, where the opposition has a majority, could reject the measures within the next 30 days, the PiS-dominated lower house would likely adopt them again before sending them for final approval to Duda.

Critics including constitutional experts claim the new measures violate Constitutional Court rulings stating that changes to the election code must be adopted at least six months before voting day.

An EU member of 38 million people, Poland has recorded 1771 confirmed cases of coronavirus, including 20 deaths.

It shut borders and schools earlier this month and has since limited public gatherings to two people and restricted freedom of movement in line with EU-wide measures to stem the spread of COVID-19.