Celebrity Extinction Rebellion supporters have admitted in an open letter being "hypocrites" over their high-carbon lifestyles.
But stars including Benedict Cumberbatch, who last week joined London protests, called for "systemic change" to the "fossil-fuel economy".
It comes as Extinction Rebellion was granted permission to challenge a London-wide protest ban in court.
Several demonstrators have been arrested as hundreds defied the ban.
More than 100 celebrity supporters of Extinction Rebellion signed the letter to the media, which urges the media to focus on "the real story" of the climate and ecological emergency.
Spice Girl Mel B, comedian Steve Coogan, musician Bob Geldof, actor Sir Mark Rylance, model Lily Cole and Glastonbury's Emily Eavis, among others, all confessed their culpability in the climate crisis.
The letter says: "Dear journalists who have called us hypocrites. You're right.
"We live high carbon lives and the industries that we are part of have huge carbon footprints.
"Like you, and everyone else, we are stuck in this fossil-fuel economy and without systemic change, our lifestyles will keep on causing climate and ecological harm."
But they called on the media to focus on the "more urgent story" of life on earth dying in a sixth mass extinction.
They said they cannot ignore the call of young people such as Greta Thunberg to "fight for their already devastated future", even if it means putting themselves "in your firing line".
Meanwhile, the prime minister is to chair a new cabinet committee on climate change to drive action to cut emissions across the government. Green groups have been calling for such top-level co-ordination - although they remain critical of other policy details.
It comes as police have begun making arrests after Extinction Rebellion activists defied an order banning them from demonstrating anywhere in London.
About 500 protesters gathered in Trafalgar Square, some of whom covered their mouths with black tape to symbolise the silencing of their protest.
Within a couple of hours, the protest broke up and large numbers dispersed. Police arrested a small group who were blocking Whitehall, BBC correspondent Andy Moore said.
Among those arrested were Green Party co-leader Jonathan Bartley and George Monbiot, the author and Guardian journalist.
As he was arrested, Mr Monbiot said: "We have to make a stand against the destruction of our life support systems."
An application for a judicial review of the ban was accepted by the High Court, according to an Extinction Rebellion spokesman.
It means the case can go ahead, with an initial hearing scheduled for Thursday.
The claimants include the Green Party's Caroline Lucas and Baroness Jenny Jones, Labour MPs Clive Lewis and David Drew, and Mr Monbiot.
Extinction Rebellion argues the ban is disproportionate and an unprecedented curtailment of the right to free speech and free assembly.
The group hopes the High Court will quash the decision to implement the blanket ban.
It follows the Metropolitan Police announcing new restrictions under Section 14 of the Public Order Act, which required protesters to disperse by 21:00 BST or risk arrest.
Any assembly of more than two people linked to the Extinction Rebellion action is now illegal in London.
The force said it decided to impose the rules after "continued breaches" of conditions which limited the demonstrations to Trafalgar Square.
More than 1,600 people have been arrested since the protests, dubbed the Autumn Uprising, began on October 7.
Deputy Assistant Commissioner Laurence Taylor, who is leading the policing of the demonstrations, said he was confident the Met's decision was "entirely lawful" and "entirely proportionate".
Also on Wednesday, a group of mothers and babies defied the restriction, staging a "feed-in" outside Google's offices in London's King's Cross, while other activists targeted the nearby offices of YouTube - a Google subsidiary.
They said they wanted to highlight the company's political donations to organisations that have campaigned against action on climate change.
Labour leader Jeremy Corbyn said concerns had been raised about the police's decision to ban the protests, adding that shadow home secretary Diane Abbott was discussing it with the police.
"I think it's important to protect the right of free speech, and the right to demonstrate in our society - obviously in a non-violent way," he said.
He added that Labour's London Mayor Sadiq Khan had no involvement in the "operational decision" by police to remove the protesters.
On Tuesday, Mr Khan said he was "seeking further information" about why the ban was necessary, saying he believed "the right to peaceful and lawful protest must always be upheld".
A government spokesman said the UK was already taking "world-leading action to combat climate change as the first major economy to legislate to end our contribution to global warming entirely by 2050".
"While we share people's concerns about global warming, and respect the right to peaceful protest, it should not disrupt people's day-to-day lives," he added.
What are the rules around protests?
Police have the powers to ban a protest under the Public Order Act 1986, if a senior officer has reasonable belief that it may cause "serious disruption to the life of the community".
Police are also under a duty to balance the task of keeping the streets open with the right freedom of assembly under Article 11 of the Human Rights Act 1998 and freedom of expression, under Article 10. These rights are not absolute - the state can curtail them.
However, the BBC's home affairs correspondent Dominic Casciani said: "The test, if and when it gets to a human rights court battle, is whether police action was proportionate to the threat and only what was strictly necessary."
By law, the organiser of a public march must tell the police certain information in writing six days in advance.
Police have the power to limit or change the route of the march or set other conditions.
A Section 14 notice issued under the Public Order Act allows police to impose conditions on a static protest and individuals who fail to comply with these can be arrested.