Young climate activists turn up the heat on Keir Starmer

Going into the next general election, Labour's plan to pour billions of pounds into clean energy will be one of the clear dividing lines between it and the Conservatives.

A pledge to invest £28bn a year in green industries is one of Labour's five national missions, and a key plank of the "greener, fairer future" it has promised.

It gave climate activists reasons to be excited by Labour.

But last month, Labour announced it was delaying its spending commitment until the second half of its first term in government, blaming the UK's bleak economic outlook.

Many climate activists were furious, and during a recent speech in Gillingham, Labour leader Sir Keir Starmer felt their wrath.

Several minutes into his speech, two activists from Green New Deal Rising unfurled a banner behind him. "No more U-turns. Green New Deal," it read.

Sir Keir assured the activists he would meet them to discuss their demands, as they were hastily ushered off stage.

More than a week on, the meeting still has not happened and now activists from the group are lining up fresh attempts to grab his attention.

On Friday, activists staged sit-outs outside the constituency offices of Sir Keir, shadow chancellor Rachel Reeves and deputy leader Angela Rayner. They plan to continue these protests until Labour's annual party conference in October, and are not ruling out further disruption - including interrupting speeches - if Sir Keir fails to meet their demands.

"We're escalating our campaign against Labour now, because we want to influence their manifesto," says Hannah Martin, co-director of Green New Deal Rising.

"We want what they offer to voters to be something bold."

Labour says it is already offering voters something bold - a plan to turn Britain into a "clean energy superpower".

The plan involves creating a publicly-owned energy company, insulating millions of homes, and using a national wealth fund to build green industries.

"Labour is the only party with a long-term mission to make Britain a clean energy superpower to cut bills, create jobs, provide energy security, and tackle the climate emergency," a Labour spokesperson said.

The BBC has been told Green New Deal Rising has been offered a meeting with party officials, but has shown no interest.

Instead, the group appears to have its sights set on Sir Keir and those at the top of the party. With no time for a chat in Gillingham, the wait for a meeting goes on.

"We were removed from the building," says Sophia Coningham, one of the activists involved in the Gillingham stunt.

She says they gatecrashed the speech to remind Sir Keir that, "to really stand up for young people, they need to commit to a green new deal".

"There's a feeling that Labour is backsliding," says Ms Coningham, an 18-year-old who has just finished her A-levels.

So what is a green new deal?

Campaigners say it's a set of policy proposals to address the root causes of climate change while promoting a more sustainable model of economic growth. It harks back to the New Deal economic programme of 1930s US president Franklin D Roosevelt, and more recently, it's an idea that's been revived and modernised by Democratic politicians in the United States.

Back in the UK, the idea has been floating around for more than a decade, with campaign groups and left-wing MPs - including Labour's shadow climate change secretary Ed Miliband - calling for different flavours of a green new deal.

For the Conservatives, what they see as the economic dangers of funding such green policies through borrowing have been deployed as a political attack line against Labour.

By the time Green New Deal Rising emerged in 2021, the notion of an economic approach centred on clean energy had entered the political mainstream.

Even so, since its launch, the group of about 500 organisers and young climate activists has been lobbying Labour and claims its campaigning has influenced the party's energy policies.

Now it is trying to push Labour to go even further.

"Part of why we took action last week was that we want to see a future government that's committed to the green new deal," says Ms Martin. "We're not going to be silent."

In a campaign targeted at Labour, Green New Deal Rising has put five demands to the party. One Labour source argues that two of the five demands - "expand public ownership" and "tax wealth now" - are not related to green policies.

The other three demands include creating more green jobs, setting up a national nature service, and making polluting companies pay.

"What they're asking for isn't radical," says Labour MP Clive Lewis. "If you look at the science, and what that's showing us on climate change, then their asks are quite mild."

He describes recent briefings against activists as "attempts by some close to the [Labour] leadership to put some distance between them and the climate movement".

Mr Lewis says he hopes activists from Green New Deal Rising have "done everything to engage with Labour MPs" before resorting to disruptive tactics.

"If they feel they have no option but to do this, then that's their prerogative," he says. "The danger is that this pushes politicians into a corner where they might react in a negative way. Politicians are human."

If disruptive tactics became more commonplace, it's possible a more antagonistic relationship could develop between Labour and climate activists.

That could risk alienating some younger voters, as Ms Coningham explains.

"I think Labour has to earn my vote and that means signing up to our demands," she says. "Labour need to stop taking young people's votes for granted."

Voters from younger generations who care about the climate are a big constituency and one that Labour will want to win over. As things stands, a more radical Labour plan on energy and climate seems unlikely, given the financial discipline the party has been signalling.

But with the Labour manifesto yet to be completed, there is still time for minds to be changed - and a meeting or two perhaps.