Inspired by a wave of youth activism, scouts from across Britain are setting aside campfires and hobby badges to tackle some of the UK’s biggest social issues, from homelessness and the climate crisis to migrants and mental health.

The 112-year-old movement has enlisted the support of British astronaut Tim Peake to lead its campaign, in part spurred on by the 16-year-old Swedish activist Greta Thunberg.

“She inspires me with her passion,” says 19-year-old scout Sam Murphy from Salisbury. “To see a young person taking a stand on that sort of level, it’s amazing – you look at her and go, if she can do it why can’t I?”

The scouts themselves chose the issues they wanted to take on in a vote among their 640,000 members. The campaign kicks off next week with a focus on Britain’s homeless in partnership with the charity Crisis.

As a former scout himself, it was easy for Peake to get on board. He says being a scout was one of the factors that inspired him to become an astronaut. Young people can make anything happen if they believe, he says.

“They’re leading the way. They’re the doers, the give-it-a-goers, the change makers – they’re not afraid to take a deep breath and speak up,” he will tell MPs in a speech to launch the campaign on Monday.

Astronaut Tim Peake, a former scout, will lead the campaign. Photograph: James Gillham/REX/Shutterstock

Scouts will work to raise awareness of the issues with help from charities such as Mind, the National Autistic Society and the British Red Cross. “We’re united in our belief that we can make change happen,” Peake will say.

There’s nothing new in scouts doing community projects – but championing displaced children or lobbying MPs for a solution to homelessness are a world apart from the litter tidy-ups and village fetes they are typically associated with.

Young people are getting “louder and louder” says Sam. “It feels like we’re really starting to make some noise.”

Chief scout Bear Grylls believes it is not just noise but what he calls “a shift in the balance of power”. “Greta (Thunberg) has shown young people that their voice can be heard,” he says. “The most compelling and trusted voices are no longer coming from the establishment, but from young people. When they see injustice, they call it out. When they see threats to our planet, they call it out. They want to see a brighter future and they’re not prepared to wait for it.”

The issue of homelessness is particularly poignant because the scouts say it affects their everyday lives. “They’re seeing people they know – maybe a friend, an elder sibling, someone in their community – ending up on the streets, in quite insecure situations,” says Jon Sparkes, chief executive of Crisis. “So they’re thinking about their own futures.”

Sparkes says the cost of housing, cuts to housing benefit and pressure on the welfare state have become issues that young people are seeing much more clearly than previous generations.

Chief scout Bear Grylls is behind the campaign. Photograph: Channel 4

That resonates with Sam Murphy. One of his best friends was homeless for six months, he says. “It was scary – he refused to go into a shelter because he didn’t feel it was safe.”

Murphy’s scout group want to help build bridges with homeless people and plans to host community dinners where they can feel “more connected with the community”.

Sophie Maxwell, who lived on the streets as a teenager, says the scouts could make a difference because of their sheer numbers. Some of the older ones could “buddy” people who are homeless, she says.

Maxwell, who now runs the Really Neet Project in Sheffield, a learning establishment for disadvantaged young people – cautions though that there are “deep-seated issues” and they won’t be resolved overnight.

“It’s great the scouts are getting involved, but we need systemic change if we are to tackle this issue”, she says.

In Enfield, north London, at a pilot session for the new campaign, young beaver scouts are using balloons to simulate choices that homeless people have to make, such as taking a shower or buying food.

The children – five- and six-year olds – have to move the balloons around and talk about the choices they would make in their own lives.

“If I didn’t have a home, that’d be pretty scary, especially at nighttime,” says five-year-old James Thorpe.

“We should try to help the homeless so they know they’re not alone and they know people care. I’m only five so I’m going to speak to my leader and see what we can do.”