The European Commission has published the first set of criteria for companies to be labelled as green under its sustainable finance taxonomy regulation.

The rulebook so far covers the economic activities of roughly 40% of listed companies in sectors that are responsible for almost 80% of direct greenhouse gas emissions in Europe, the commission said. They include sectors such as energy, forestry, manufacturing, transport and buildings.

Whether and how to include natural gas in the taxonomy will be addressed in a separate proposal later this year, while nuclear energy is being reviewed separately.

The EU's green taxonomy, which is due to come into practice from 2022, will work as a guide for investors to assess sustainable projects and enhance the reliability and comparability of sustainability information. The hope is that it will help to unlock the private investment needed to make the EU economy carbon neutral by 2050.

The new rulebook introduces performance criteria for determining which economic activities "contribute substantially to climate change mitigation and adaptation," the commission said.

It said it will be "a living document," meaning it will evolve over time and more activities will be added to its scope. Another set of criteria will be adopted later in 2021 on agriculture and other energy sectors not yet covered by the document.

EU countries have been split over whether gas-fueled power plants should be deemed green. Some stakeholders see it as a potential transitional activity facilitating the switch from coal and oil to renewables, and thus argue that it should be recognized in the taxonomy.

The commission said its proposal later in the year will cover natural gas and related technologies "as transitional activity in as far as they fall within the limits of the EU Taxonomy Regulation" and said it will also consider legislation covering gas activities that can help to reduce emissions but cannot be covered within the EU taxonomy.