Poland's biggest opposition group, the European Coalition, plans to eliminate coal from power production by 2040, its leader said on Saturday as he unveiled pledges ahead of an autumn election to be fought against the coal-friendly, conservative government.

Poland generates electricity mostly from coal and has some of the worst air quality in Europe. The ruling Law and Justice (PiS) party, which won a 2015 election partly on promises to sustain coal, plans to cut the use of the polluting fuel to around 60 percent by 2030 from around 80 percent now.

"We are committed that by 2030 we will eliminate coal in household heating, by 2035 in systemic heating and by 2040 in the energy sector," Grzegorz Schetyna, the European Coalition leader said in a televised speech at the group's convention.