Some campaigners fear governments will shy away from long-term efforts to curb emissions or lift the carbon costs they impose on polluting sectors in a bid to relieve firms hit hardest by the outbreak.

"The Green Deal is not over ... We should deliver and we should work on greener solutions," Thierry Breton, the European Commissioner for the 27-country EU's internal market, told an online event.

Coronavirus will inevitably change these discussions, but this should not come at the expense of decarbonisation, he said.

European companies were reviewing their operations to address issues including carbon costs before coronavirus disrupted supply chains, Breton said.

Only nine days ago, the EU unveiled a plan to steer industry towards the bloc's goal to cut net greenhouse gas emissions to zero by 2050 -- a target that will require huge investments to retrofit factories with low-carbon equipment.

Since then, companies including ArcelorMittal, the world's largest steelmaker, and German carmaker Volkswagen, have said they will scale back production in Europe amid supply chain disruptions and sinking demand.

Lower production means Europe's industrial emissions are expected to fall by more than 20 million tonnes of carbon dioxide this year, consultancy Energy Aspects told Reuters, revising a previous forecast from Monday that industrial emissions would dip by 10 million-20 million tonnes this year.

EU carbon prices have tumbled amid the pandemic, reducing the price of pollution permits firms must buy to cover their emissions. But the drop in carbon prices could also mean less funding is available to help industrial sectors decarbonise.

One source of support is an EU innovation fund made up of revenues from carbon allowance auctions in the coming years that was valued at some 11 billion euros (10.3 billion pounds) at the end of 2019, when the EU carbon price was roughly 25 euros per tonne of carbon dioxide.

Carbon prices are now nearer 16 euros per tonne, putting the fund's value at roughly 7 billion euros.

(Reporting by Kate Abnett; Editing by Catherine Evans)