Swedish teenage climate activist Greta Thunberg lashed out at the Danish capital because Copenhagen has for the last six years pumped large amounts of wastewater into the strait separating Sweden and Denmark.

Danish media, citing the Danish Environmental Protection Agency, say that since 2014, over 35 billion litres of unfiltered sewer water have been pumped into the Oresund Strait during heavy rains because Danish treatment plants could not handle the large volume of water.

The information has surfaced recently because the capital had planned to allow the Greater Copenhagen Utility Hofor to flush 290,00 cubic metres of unfiltered wastewater into Oresund starting on Sunday.

That decision has been postponed until October.

Greta said on Facebook that these actions are coming from “the same Copenhagen who claim they’ll be climate neutral by 2025”.

The Danish capital aims to become carbon neutral by 2025, possibly the first world capital to do so.

The 17-year-old has encouraged students to miss school to join protests demanding faster action on climate change, a movement that has spread beyond Sweden to other European nations and around the world.

She founded the Fridays for Future movement that has inspired similar actions by other young people.