Rishi Sunak’s government will “go down in history” as the administration that failed the UK on the climate crisis while ministers pursued a dangerous culture war, the heads of Greenpeace have said. The charity’s joint executive directors described government briefings against the organisation in the wake of its oil protest at the prime minister’s Yorkshire home as “really dark stuff”, which revealed a worrying trend towards exploiting environmental protests as a wedge issue. In an interview with the Guardian, Areeba Hamid and Will McCallum said an “unprecedented” move to block the organisation’s policy experts from advising civil servants could have disastrous consequences for environmental policy. Greenpeace is the world’s highest profile environmental NGO. Last Thursday its activists draped Sunak’s Yorkshire manor house in black fabric to protest against his intention to “max out” the UK’s oil and gas reserves with a new round of licences for intensive North Sea drilling. The organisation said it planned the protest carefully to coincide with the Sunak family’s trip to California when they knew the house would be empty. They have carried out such targeted environmental stunts before – at Sunak’s home and previously at David Cameron’s and John Prescott’s houses – but said this time the political response was more aggressive. Conservative MPs spoke about the peaceful stunt in the same breath as the murders of the MPs David Amess and Jo Cox. Hamid said “retribution was swift” in the wake of the protest, with important meetings cancelled after ministers told government officials to cease all engagement with the group. They said a planned meeting about plastics with senior civil servants this week was pulled and the organisation was ejected from a WhatsApp group with civil servants planning a meeting with NGOs on ocean protection, a subject on which they have “decades” of policy expertise. McCallum said: “Locking us out is really just denying civil servants a way of engaging with a civil society group that is desperately trying to make sure they are equipped to go into negotiations in the UN, for example, on deep-sea mining, or whatever the issue happens to be. So it is worrying.” The organisation’s leaders have also published an open letter to Sunak, which was sent to him on Thursday. They told the prime minister that his “response to stonewall further communication sends a worrying signal about the government’s commitment to climate action, as well as the future of our democracy”. The letter accused Sunak’s government of adopting “more and more of a bunker mentality” in recent years and refusing to engage with civil society experts. They asked the prime minister to sit down with them and discuss “solutions for reducing the UK’s dependence on fossil fuels while tackling the cost of living crisis”. The government has said in briefings that it does not think those “accused of breaking the law should have a seat at the table” in discussions with them. But the directors said Sunak’s government was simultaneously risking undue influence from “corporate polluters” who themselves broke the law. The letter says that in a six-month period, the Department for Energy Security and Net Zero and formerly the Department for Business, Energy and Industrial Strategy, met BP and Shell 12 and 11 times respectively “despite both companies’ repeated history of unlawful activities”. Shell’s subsidiary was found responsible for two major oil spills in Nigeria by The Hague court of appeal last year, and BP pleaded guilty in 2012 to criminal misconduct in the worst US offshore oil spill in history. McCallum said of ministers: “They’ll go down in history as the government that failed us. 2023 is going to be the year that we look back on as when extreme weather became the norm. They failed us in our time of greatest need.” He said ministers had not been engaging with green groups for a long time but that it was new and “worrying” to have access to civil servants blocked. “The reality is ministers haven’t been meeting with green NGOs throughout this government. Definitely it is a step further to extend this to civil servants. And from what we hear, it’s worrying. We provide evidence. Yes, we’re famous for taking action and doing protests, and it’s action and protest that’s got into the news. But we do all kinds of other work.” McCallum said there had been “really dark stuff coming up from people in very senior positions of power. What we did was drape a curtain over an empty house at the time of a climate crisis and send a message. And the way that some of them have reacted in the same breath, likening it to attacks of all kinds, that’s not on. They know Greenpeace, we have always abided by our principles of non-violence. “We’ve been to politician’s houses before and not met with this kind of response,” he said, describing it as “faux moral outrage”. He added: “We need some really serious people in this cabinet at the moment and it doesn’t feel like we’ve got them.” He and Hamid, who started as Greenpeace co-directors last October, said the protest had been polarising, both losing and gaining them donors, but insisted it would not deter them from pursuing direct action. “The worst thing we can do in an onslaught against direct action and legitimate civil disobedience would be to stop doing it; you’ve got to carry on,” McCallum said. But the pair acknowledged that the ferocity of the response meant it would be counterproductive to target an MP’s home again any time soon. Briefing against the group has also been politicised, with stories in the press calling Labour’s Mid Bedfordshire byelection candidate, Alistair Strathern, a “Greenpeace zealot” for taking part in a protest outside the Home Office dressed as a zombie last November. The organisation plans to branch into community organising before the election, launching a project they are calling “Operation Climate Vote” which will mobilise thousands of volunteers around the country to canvass 1m homes. They want to explain the potential for politics to address climate change and persuade people to vote according to environmental policies. Hamid said: “The antidote to what’s happening with culture wars is to actually go down and have those conversations with real people instead of fighting Twitter wars between hashtags and terrible slogans.” She added: “I get asked all the time: what is the one thing individuals can do? I would say, vote for the climate hawk. That’s the thing. Personal responsibility, making personal choices, that is all well and good. But if you want change, the next election is to vote for the climate hawk. There is hope because we can turn this around.” A government spokesperson said: “Greenpeace’s criminal activity last week demonstrates that they are not a serious organisation. “We make no apology for taking the right approach to ensure our energy security, using the resources we have here at home so we are never reliant on aggressors like Putin for our energy, and our approach supports 1,000s of British jobs. We have also decarbonised faster than any other G7 country, are investing billions into renewables which now account for 40% of our electricity, and we have the four largest windfarms in the world in the UK.”