Polish environmental groups on Friday filed a complaint with the European Union against national and local authorities for failing to fight lethal levels of smog.

The European Environmental Agency (EEA) blames air pollution -- caused in large part by the burning of coal -- for an estimated 50,000 premature deaths per year in the country of 38 million people.

Seventy percent of Polish households burn low-quality coal or rubbish in old stoves for heating.

Antiquated coal-fired power plants generate nearly all of Poland's electricity, giving it some of the most toxic air in the 28-member EU.

"Poland has Europe's highest air-borne concentrations of the carcinogen benzopyrene -- norms are exceeded four-fold -- breaching both Polish and EU laws," Piotr Cykowski, an activist with the Action Democracy NGO told AFP at the European Commission branch office in Warsaw.

"This is why we're filing a formal complaint to the European Commission which could formally sanction Poland for inaction in fighting lethal smog," he added.

"We were expecting the introduction of a ban on the sale of the lowest quality coal for domestic heating purposes. However, new draft regulations change nothing," said ClientEarth Poland lawyer Agnieszka Warso-Buchanan, noting that the government admits that "a ban would harm the coal industry."

Poland's current rightwing Law and Justice (PiS) government and previous administrations of all political stripes have based energy policy on plentiful domestic coal, while taking little action to mitigate pollution.

Smog has spiked to record levels nationwide in recent years, with windless days this winter causing particularly acute pollution.

A public petition signed by 24,000 Poles backed the formal complaint filed by the NGOs, including global environmental groups Greenpeace and ClientEarth as well as activists from the local Action Democracy and the City is Ours groups.

The European Commission said in an environmental review of Poland published this month it was already "launching infringement procedures" against Poland and other members over "persistent breaches of air quality requirements... which have severe negative effects on health and the environment.

"The aim is to put in place adequate measures to bring all zones into compliance."

The report also estimated that "the health-related external costs from air pollution in Poland are above 26 billion euros ($28 billion) per year.

"These direct economic costs include the 19 million workdays lost each year due to sickness related to air pollution."

It urged Warsaw to "establish emission standards for coal-fired individual heaters" among other measures "in order to mitigate risks."