About 5,000 people supported the proposal to reduce the working day in Poland from eight to seven hours.
A bill drafted by the left-wing Together (Razem) party has since Monday gathered 5,000 signatures of the 100,000 needed if it is to be considered by parliament.
Under the proposed changes, the working week would be shortened gradually, to 38 hours in 2019, 37 in 2020 and 35 in 2021, while keeping incomes unchanged.
“We work far too much. We even spend more hours at work that people in Japan, which has always been considered a country of overworked people,” the Together party’s Marcelina Zawisza said.
She said well-rested workers “fall ill less frequently and work more efficiently.”
The party’s spokeswoman Dorota Olko said: “People know full well that people abroad work less for decent pay.”
She said France had benefitted from seven-hour working days.
“If we really want to have a modern economy, it is high time we went in that direction,” she said, adding that it would lead to greater efficiency.
According to the Organisation for Economic Co-operation and Development (OECD), Poles spent 1,928 hours at work in 2016, the second most in the European Union after Greece.
The average includes people who work part-time or seasonally as well as leave taken for holidays, illness and other reasons.