An Extinction Rebellion protester dressed as a bee has glued himself to the Liberal Democrats’ battlebus, as the environmental group intervenes in the general election.

The group said it was “buzzing around” political parties’ campaign battlebuses on Wednesday “demanding the climate and ecological emergency is top of the agenda this election”.

The incident took place outside the Knights youth centre in Streatham, south London, after the electric-powered Lib Dem battlebus arrived. As activists waited for the Lib Dem leader, Jo Swinson, who was travelling separately, about half a dozen activists dressed in yellow-and-black bee outfits ran down the road towards the bus.

One man glued his hand to the windscreen, and smeared ketchup on the glass. Others handed out flyers and debated with Lib Dem activists.

Facebook Twitter Pinterest View from inside the battlebus. Photograph: Aaron Chown/PA

One activist, Linda Doyle, said the Lib Dems’ plans to tackle the climate emergency were too weak. “The Lib Dem policy is 2045 for greenhouse gas neutral, which is really just disgraceful,” she said. “We’re here at a youth centre. I don’t see how they can help the youth whatsoever unless they provide them with a future.”

Police blocked the road, establishing a cordon to keep people away from the bus. But when Swinson arrived she was allowed to speak to activists. She claimed her party’s plans were as ambitious as possible.

Speaking to reporters at the youth centre, Swinson said there was “clearly a little bit of irony in glueing yourself to an electric bus”, but said she did not object to the protest.

“I welcome that the climate emergency is a really important issue in this election,” she said. “We can have a discussion about how quickly we can get there – that’s a good discussion to be having, a genuine debate about how quickly we can deal with the climate crisis.”

She defended her party’s climate targets as ambitious but realistic, saying they could be reviewed as technology improved.

She said: “The most important thing is that we get as much carbon dioxide out of our emissions as quickly as we possibly can, and ramp up that programme of planting trees so we can take carbon out of the atmosphere.”

XR is targeting all the parties in the election. In a statement, the group said: “The protest, going by the name ‘Bee-yond Politics’, is being carried out to remind politicians of the irreplaceable biodiversity loss that is a direct result of their poor, irresponsible policymaking.

“Activists wanted to plant the plight of bees and other pollinators fully in the minds of the next prime minister, and to remind them that they hold the future of life in their hands. Our bee population is being threatened by extreme weather and habitat destruction, bringing with it crop instability and food vulnerability.”