Extinction Rebellion activists dressed as bumble bees have targeted the campaign, swarming around their battle bus, with one even gluing themself to it in protest against the party's climate policies.
The group said six of its activists had targeted Jo Swinson's battle bus, during a visit to Knights Youth Centre in London, to demand that the "climate and ecological emergency is top of the agenda this election".
"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 policy-making," they added.
ITV News Correspondent Rebecca Barry reported that police arrested one protester after a member of the group super-glued themself to the Lib Dems bus.
Other members of the group swarmed around the bus citing their climate demands.
Ms Swinson spoke to two of the activists, saying she attended an Extinction Rebellion protest earlier this year and understands it's an "important cause".
She said: "I've been to the Extinction Rebellion protest myself earlier this year because I think it is a really important cause."
Ms Swinson added: "I think it's absolutely true that we are facing a climate emergency, we are in that now."
When pushed on when her party will get to carbon net zero, she said: "That can be done by 2045 but should be more ambitious and try to do it quickly and the other thing is, it's not about the year in which you get to net zero, it's about how quickly you make the cuts right now."
Speaking after the event Ms Swinson again stressed the importance of the "climate emergency", but criticised the protesters' actions.
"There is clearly a little bit of an irony in gluing yourself to an electric bus," she said.
"A little bit like when the DLR was targeted.
"Obviously, again, a fairly environmentally friendly form of transport.
"But I recognise the general point.
"I welcome that the climate emergency is a really important issue in this election."