Appeal court judges have ordered the Dutch state to step up efforts to cut CO2 emissions in a case brought by campaign group Urgenda.

The state appealed against a decision three years ago that required it to reduce greenhouse gas emissions by 25% of 1990 levels by 2020. It was the first time a court had ruled that a national government was legally bound to follow through on promises made in international climate agreements.

Lawyers for the state argued that the district court in The Hague should have left the decision to parliament, but the appeal court found in favour of Urgenda. Judges said the state had a ‘duty of care’ to protect its citizens from the impact of climate change.

On current prognosis the Netherlands is on course to reduce CO2 emissions by only 23% of 1990 levels. The government must now decide what measures it should take to speed up the process. Potential solutions include closing coal-fired power stations sooner or reducing the speed limit to 120 km/h on motorways.

The court cited a report published by the UN climate change panel IPCC in 2007 which said developed countries needed to reduce CO2 emissions by between 25% and 40% in order to stop global temperatures rising by more than 2 degrees celsius.

The IPCC said in a new report on Monday that the Netherlands would have to strengthen its sea defences to counter a projected rise in sea levels of 30 to 60cm.

The state can appeal to the Supreme Court against Thursday’s judgment, but with less than 18 months to go until the deadline it cannot afford to ignore it altogether.

Marjan Minnesma, director of Urgenda, said the judgment was an ‘incredible blow to the state.’ ‘The judge was extremely firm and found for us on every point.

‘This has been followed around the world, so it gives hope to lots of people worldwide to think: we can do this too. This is the only democratic way to ensure governments speed up their efforts.’