A group of climate change activists scaled the gates of Buckingham Palace and secured themselves to the railings on Saturday.
Four protesters from the Climate Siren group locked themselves to the south centre gate just after 2pm, wearing t-shirts bearing the words "climate emergency. 10% annual emission cuts" and wielding megaphones.
Two of them held a banner carrying a quote from the Prince of Wales reading: "The doomsday clock of climate change is ticking ever faster towards midnight. We are simply not reacting quickly enough."
Other activists wearing t-shirts and carrying banners with the same message were also on the scene.
The group said they were calling on the Queen to follow her son's example in speaking out about "the escalating threat of catastrophic climate change".
The protest came the day after the Rio+20 global conference on sustainable development in Rio de Janeiro, Brazil, came to a close.
The group described their actions as "an act of civil disobedience designed to demand urgent, concerted and meaningful action to tackle the unprecedented national and global emergency presented by the catastrophic destabilisation of global climate and timed for the day after the end of the Rio+20 Earth Summit in Brazil."
They said they had vowed to protest against "the failure of the conference to achieve any meaningful results".
In an open letter to the Queen posted on their website, Climate Siren said their protest was to demand "a fundamental upscaling of our national effort to confront the emergency presented by catastrophic destabilisation of global climate".
They had chosen to mount it outside Buckingham Palace to emphasise that the issue was of "critical importance for our national destiny" as well as for the future of the entire global community, they said.
The letter read: " We are calling for our nation to take strenuous, positive action both to fulfil our responsibilities as a major emitter of greenhouse gases, now and historically, and to show courage and resolution in taking a lead on the issue, if necessary.
"We echo the sentiments of your son and heir, HRH the Prince of Wales ...
"But we are going further because such sentiments are in danger of becoming mere platitudes if not accompanied by concrete proposals for action."
They told the Queen she was from a generation that can remember "another great national struggle" and wrote: "We believe that our national security is at stake now, no less than it was during the dark days of the last Great War, albeit in a very different way.
"As you celebrate this year's Jubilee you must find it impossible not to view with consternation the dark clouds that once again are gathering to threaten the future of this island, with which your name has been so closely associated these last 60 years.
"These are the dark clouds of what looks increasingly likely to be a much greater global tragedy than the last World War.
"It is time to act - with boldness, resolution and determination - not the kind of half-hearted half-measures that we have seen up to now."
Activist Siobhan Grimes, 24, from Bethnal Green in east London, who was among those at the scene, said: "Our politicians aren't doing enough. We're hoping to inspire people to wake up to the consequences of catastrophic climate change."
The Prince of Wales issued his warning that action on climate change was not being taken quickly enough in a speech to the European Parliament in Brussels in February 2008.
The activists chained to the gate were said to be Fiona Brooks, 23, Cyril Zeldine, 33, teacher Peter Coville, 45, and Phil Thornhill, all from London.
"Bearing in mind the message published at the end of the three day conference I convened in London three years ago, you will not be surprised to hear that the message of your event today - that there has to be proper recognition of the peril we are in - is one I agree with wholeheartedly. "
A Metropolitan Police spokesman said: "At approximately 2.05pm a number of protesters climbed the south centre gate at Buckingham Palace and secured themselves to the railings. Police are on the scene."
Police sent a cherry-picker to start removing the protesters from the gate just before 6.30pm.