Greenpeace protesters briefly blocked the route of Boris Johnson as he was driven to meet the Queen, demanding he "get to grips with the climate emergency".
The activists, wearing sashes reading "climate emergency", held hands to form a human chain across the Mall in central London, holding up the vehicle taking Mr Johnson for his meeting at Buckingham Palace.
Greenpeace UK executive director John Sauven tried to hand Mr Johnson the environmental group's 134-point climate emergency manifesto detailing the wide-ranging policies it believes the new administration must implement.
The group wants an emergency budget to put the UK on a path to net zero emissions, and for the Government to stop supporting "damaging" projects such as Heathrow expansion.
It also wants the new Prime Minister to introduce "gold standard" environmental laws, guarantee a just transition so workers can switch from high to low carbon jobs, and show international leadership on climate change.
The action by Greenpeace is the latest in a growing wave of protests calling for action to tackle the climate and environment emergency, with school strikes by children and disruption by Extinction Rebellion.
Greenpeace campaigners also interrupted the Chancellor's speech at Mansion House in May.
Mr Sauven said: "Climate change needs to be front and centre of this new administration from day one. The responsibility on a Prime Minister to act on the climate emergency has never been greater.
"If we want any chance of leaving a habitable world to our children we need to see action start immediately. We can't blunder and bluster our way out of this emergency."
The Government has adopted a target for the UK to reach "net zero" greenhouse gas emissions by 2050.
But its advisory Committee on Climate Change has warned the country was already off track to meet its carbon-cutting targets before the new tougher goal was made law.
After the protest, Mr Sauven told PA that he thought there would be a lot of pressure on Mr Johnson to act on climate and the environment.
He said: "We want a green economy, we want green jobs, we want a healthy environment – this is really what [Mr Johnson] should be talking about now."
He added: "He has very little mandate with such a slim majority but I think
even the Conservative Party understand if they want votes in future they can't
start denying that the environment is beginning to be the top of people's
"People are really concerned about climate change."
And he said: "People are beginning to see the reality of what climate change in
future is going to mean for their lives and their livelihoods."
"I think there's going to be a lot of pressure on him to act."