Poland will close its coal mines in the coming decades as phasing out the fossil fuel is inevitable in light of the European Union's climate policies, Deputy Prime Minister Jacek Sasin said on Thursday.

Poland generates most of its electricity from burning coal, which has become costly due to rising prices of carbon emission permits. The industry has also struggled with falling demand for coal, which accelerated during the COVID-19 lockdown because the country used less power.

On top of that, many miners caught COVID-19 and some mining operations were temporarily closed or reduced.

The government, together with coal mining trade unions, aims to work out a restructuring plan for the industry by the end of September. It had planned to close two coal mines, but dropped the plan following pressure from the unions.

"The process of closing mines is inevitable, as it is very much related to the EU's energy and climate policies. This process will last for a few decades and over that period coal mines will be closed," Sasin told private radio RMF.

Poland is the only EU country that has not pledged to be carbon neutral by 2050, with the ruling Law and Justice (PiS) party arguing it needs more time and significant funds to switch to a zero-emissions economy.

But research by Greenpeace shows Poland could phase out coal by 2035 in a business-as-usual scenario.

Sasin also raised a question mark over a planned investment in a new open-pit lignite mine in Zloczew in central Poland.

"This is an issue of environmental permits. The other question is whether in 20-30 years we will need such an investment," Sasin said.