Campaigners have won a Court of Appeal ruling over controversial plans for a third runway at Heathrow Airport on environmental grounds.

Heathrow Airport said it will appeal to the Supreme Court.

Giving their ruling on Thursday, Lords Justice Lindblom, Singh and Haddon-Cave said the Government did not take enough account of its commitment to the Paris Agreement on climate change when setting out its support for the proposals in its National Policy Statement (NPS).

In a summary of the ruling, Lord Justice Lindblom told a packed court: “The Paris Agreement ought to have been taken into account by the Secretary of State in the preparation of the NPS and an explanation given as to how it was taken into account, but it was not.”

Mayor of London Sadiq Khan, who supported the legal action, welcomed the decision.

He said: “We won! Today we blocked the Tory government plans to build a third runway at Heathrow Airport. Today’s judgment is a major victory for all Londoners who are passionate about tackling the climate emergency and cleaning up our air.”

John Sauven, executive director of Greenpeace UK, said: “The court has decided that the Airports National Policy Statement is fatally undermined by ignoring climate commitments, but we still need the Government to permanently ground Heathrow’s expansion plans.

“The third runway is already on its knees over costs, noise, air pollution, habitat loss and lack of access, and now Heathrow Ltd has yet another impossibly high hurdle to clear.

“No amount of spin from Heathrow’s PR machine can obscure the carbon logic of a new runway.

“Their plans would pollute as much as a small country.

“Boris Johnson should now put Heathrow out of its misery and cancel the third runway once and for all. No ifs, no buts, no lies, no U-turns.”

Aviation Environment Federation deputy director Cait Hewitt said: “This is a huge win for the climate, and leaves Heathrow’s third runway plans in tatters.

“In presenting plans for a third runway to MPs, the Government failed, the court has found, to assess whether this was compatible with the Paris Agreement.

“The project would increase emissions at the UK’s biggest airport, and the UK has since legislated to achieve net zero emissions by 2050, so it’s very hard to see how the Government could now ever demonstrate that a third runway could be reconciled with the necessary scale of climate action.

“This ruling should mark the end of plans for any new runways in the UK. The Government should stand up to the airports lobby, drop its support for airport expansion, and invest instead in low-carbon transport and supporting British tourism.”

Will Rundle, head of legal at Friends of the Earth, said: “This ruling is an absolutely ground-breaking result for climate justice.

“We were fighting a project that would have had dire implications for present and future generations.

“We are delighted with the Court of Appeal’s ruling, which goes to show the massive importance of the legal system to check the clear abuse of state power by Government, such as in this case.

“Shockingly, this case revealed that the Government accepted legal advice that it should not consider the Paris Agreement when giving the third runway the go-ahead. The court has said very clearly that was illegal.

“This judgment has exciting wider implications for keeping climate change at the heart of all planning decisions.

“It’s time for developers and public authorities to be held to account when it comes to the climate impact of their damaging developments.”

Gareth Roberts, leader of Richmond Council, said: “This judgment is nothing short of a victory. It leaves the Government’s airports policy in tatters. It surely must be the final nail in the coffin for Heathrow’s attempts to steamroll over local and national opposition to their disastrous third runway plans.

“The expansion of Heathrow would be catastrophe for our climate and environment and for the thousands of Londoners who would be forced to live with the huge disruption it will cause.

“If the Government wants to pursue its plans for Heathrow expansion, it must now go back and revisit its own airports policy.

“Rather than the Government attempting to battle on, I hope that they will now take a minute and realise that the only way forward is for them to focus their efforts into developing a sustainable transport policy that puts the health of residents and the environment front and centre of a proposal.”

Environment minister Lord Zac Goldsmith, who lost his seat as MP for Richmond Park in the election last year before being made a peer, simply tweeted: “HUGE!!!”

Tim Alderslade, chief executive of Airlines UK, an industry body representing UK-registered airlines, said: “Today’s decision is extremely disappointing.

“The Sir Howard Davies Airports Commission spent several years looking at airport capacity in the South East and was clear Heathrow is the only game in town, with other schemes being considered and ultimately rejected.

“The economic prize is enormous if expansion is done right, with airlines ready to respond to the unlocking of new capacity by creating new routes and helping to connect the UK to new markets and destinations, and Heathrow to regions across the country.

“UK aviation has committed to net zero carbon by 2050 and this factors in the emissions created by Heathrow expansion. It is not a question of being pro-aviation or pro-environment.”

Tanya Steele, chief executive of the WWF, said: “This is a victory for the climate and for future generations who will have to live with the impacts of environmentally catastrophic infrastructure projects.

“No plan for net zero emissions, either from the UK Government or from Heathrow itself, can be credible if it includes a third runway.”

Dame Carol’s report also found interventions by the UK Government to quell the supply of drugs “have had limited success”.

The report found that the key agencies involved – the Border Force and National Crime Agency – have faced budgetary issues in recent years, however Dame Carol was unsure if extra resources would have been enough to stem the problem.

Supply of the most serious drugs – heroin and crack cocaine –  has been overtaken by the “county lines” model, which sees gangs and distribution networks from cities move into smaller towns and use violence to overtake local dealers while using children or vulnerable people to sell their product.

The report also found up to one third of people in UK prisons are there for a drug related crime – most of which are acquisitive offences.

Support in jail and for those leaving was deemed to be insufficient by Dame Carol, with those released “very likely to re-offend”.

A group of councils in London affected by the expansion, environmental charities including Greenpeace, Friends Of The Earth and Plan B, and Mayor of London Sadiq Khan, brought legal action over the Government’s approval of the plans.

Leading judges gave their ruling at 10am on Thursday, following a hearing in October last year.

Lawyers for the campaigners previously told the court that, when considering the proposals, the then transport secretary Chris Grayling did not take enough account of environmental legislation or of climate change issues.

Prime Minister Boris Johnson opposed the expansion of the west London airport when he was London’s mayor and promised to “lie down … in front of those bulldozers” to stop the runway being built.

Earlier this month he said there was “no immediate prospect” of construction beginning.

Bristol Airport’s bid to increase its annual passenger capacity from 10 million to 12 million was recently rejected by councillors due to environmental concerns.

In June last year, the Welsh Government scrapped a long-proposed £1.4 billion M4 relief road because of its cost and impact on the environment.

Anti-Heathrow expansion campaigners appealed against a High Court ruling in May, which rejected four separate judicial reviews of the Government’s decision to approve the plans.

They say the Government’s National Policy Statement (NPS) setting out its support for the project failed to properly deal with the impact on air quality, climate change, noise and congestion.

Government lawyers urged the judges to reject the appeals, arguing that the High Court reached the correct conclusion.

The appeals were heard alongside a separate challenge by Heathrow Hub, a consortium with a rival proposal for the airport’s expansion.

Support from Labour MPs helped push through the proposals to expand Europe’s busiest airport with an overwhelming majority of 296 in a Commons vote in June last year.

Mr Grayling said at the time that the new runway would set a “clear path to our future as a global nation in the post-Brexit world”.

Heathrow says it could open the third runway “between early 2028 and late 2029”.

Its previous target date was 2026.

Heathrow said the delay was due to the Civil Aviation Authority, which refused to approve its bid to nearly quadruple the amount it spends before obtaining final planning permission.

Here is a timeline of key events in the expansion project.

December 2003: A Government White Paper recommends a third runway is built at Heathrow.

November 2007: The Government publishes expansion plans. The new runway could be in operation by 2020.

January 2009: Prime Minister Gordon Brown backs a third runway despite strong opposition from local residents, environmental groups, neighbouring councils and Labour backbenchers.

October 2009: Opposition leader David Cameron tells a public meeting in Richmond, south-west London, that Heathrow expansion will not go ahead, saying “no ifs, no buts”.

May 2010: Labour loses the general election. The new coalition government of the Conservatives and the Liberal Democrats immediately scraps the third runway proposal.

March 2012: Prime Minister David Cameron and Chancellor George Osborne acknowledge the need for airport expansion in south-east England.

September 2012: An independent commission on future airport policy is set up by Whitehall. It will be chaired by Sir Howard Davies and will publish its final report in the summer of 2015.

July 2015: The long-awaited report by the Airports Commission recommends that a new runway should be built at Heathrow rather than Gatwick.

June 2018: MPs vote in favour of expansion by a large majority.

February 2020: The Court of Appeal delivers its ruling on the legal challenge to the third runway.