The government faces a legal challenge over its plan to expand Heathrow airport, with lawyers and environmentalists demanding it review its policy in line with its commitment to net-zero emissions by 2050. The Good Law Project, a not-for-profit organisation with a focus on public interest cases including environmentalism and tackling poverty, argues that the government must update its plan for a third runway to take into account the emissions pledge it made following the approval for the airport expansion in June 2018. Since the Heathrow airport national policy statement, the policy framework that governs the construction of a third runway, was published, the government has committed to a legally binding target of net-zero emissions by 2050. It also pledged to cut carbon emissions by 68% by 2030 earlier this month. The challenge follows a supreme court decision last week that the airport’s expansion was not unlawful through a failure to treat the 2015 Paris agreement as government policy. The court’s ruling, however, confined its reasoning to the legal regime of the time of the framework’s publication. It did not consider the effects of the government’s subsequent, legally binding pledge. The UK became the first major economy to set a net-zero greenhouse emissions goal in June 2019. The aim had previously been to reduce emissions by at least 80% from 1990 levels. “Setting targets does nothing to help halt climate change. We actually need to hit them,” said Jolyon Maugham QC, the director of the Good Law Project. “And that means we only approve new transport infrastructure when doing so is consistent with that target. We can’t allow climate change targets to become lies we tell to our children and grandchildren. It’s not too late to stop Heathrow expansion.” Setting the 2050 target was one of Theresa May’s last acts as prime minister, and has remained somewhat of a badge of honour for the government. Ministers routinely describe its environmental commitments as world-leading. A year on from the 2019 neutrality target, however, the Department for Business, Energy and Industrial Strategy (BEIS) was able to cite little concrete action taken to achieve the goal. Asked by the Guardian in June what measures had been introduced in the race for net zero over the past year, the department listed three points: a consultation on bringing forward the phaseout of petrol and diesel cars from 2040 to 2035, £800m for carbon capture and storage, and plans to double the UK’s international climate finance funding from £5.8bn to £11.6bn. Dale Vince, the founder of the green energy company Ecotricity and partner with the Good Law Project on this challenge, criticised the government for failing to take the bold decisions required to meet the climate targets it boasts about. He said: “This is a government that imposed a carbon tax on green energy, but exempts large users of fossil fuels, and which charges 20% VAT on solar panels for home but only 5% on coal. These are the simple anomalies that should surely not exist. The more serious ones are national planning policies which support the old way of doing things, fossil fuelled power stations and more runways. It’s a ridiculous contradiction. We should not need to go to court to fix it, but we do.”