Authors have staged a walkout from the Edinburgh International Book Festival in protest at its links to “fossil fuel companies”.

Author and climate activist Mikaela Loach interrupted her panel discussion on Saturday evening to stand against the festival’s main sponsor Baillie Gifford, accusing them of investing in “companies who make money from fossil fuels”.

It comes after more than 50 authors and and event chairs taking part in this year’s festival signed an open letter demanding organisers to find alternative sponsors if the investment management firm does not divest billions of cash.

Leading writers, including Ali Smith, Zadie Smith and Gary Younge, have threatened that if no action is taken, they will boycott next year’s event.

In a video shared by Loach on Instagram on Sunday, it showed the author stopping her discussion, titled Changing the Climate Narrative, saying: “I can’t actually in good faith continue just talking about these issues without doing something, especially give that the festival is sponsored by an investment firm that is bankrolling this climate crisis.

“Baillie Gifford are an investment firm that have £5 billion of investments in the fossil fuel industry. Edinburgh Book Festival, you wouldn’t burn books, so why are you burning the planet? Drop Baillie Gifford.”

She added that she would rather be discussing her book, It’s Not That Radical: Climate Action To Transform Our World, with her fellow authors at the event rather than having to stage the protest.

The author, who is of Jamaican descent, continued: “I think especially recently, if you look across the world, Maui is literally on fire as we’ve seen right now.

“I don’t know if my ancestral land will still be there if I have children or if I have descendants. And the reason for this is because of investments in fossil fuels.

“The reason for this is because of fossil fuel companies not caring about the climate crisis, whether they say they do or not. So, we have to remove that finance from them, any tactic that we can we have to stop them from being able to exist.”

The video then showed the audience engaging in a chant calling for Baillie Gifford to be dropped by the festival before they took their protest to the streets of Edinburgh.

Author Jessica Gaitan Johannesson, who helped organise the walkout with Loach, told the PA news agency that they staged the protest as they “care deeply about the festival and its people” and “don’t want to see it contribute to the destruction of people’s lives”.

She added: “The Edinburgh International Book Festival prides itself on facilitating discussion and being a home for storytelling.

“If conversations and stories were enough, the same festival that invites climate activists wouldn’t also be funded by money that contributes to climate breakdown.

“There is no doubt about this: wherever there is fossil fuel extraction, there is tremendous harm. This means that we need to take action beyond the page.”

In the open letter, the writers and events chairs accused Baillie Gifford of “making huge profits from global disaster” and alleged the investment management firm was seeking to “hide behind esteemed cultural institutions, like the Edinburgh Book Festival, as sanction for its continued operations”.

The letter comes in the wake of climate activist Greta Thunberg pulling out of an appearance at this year’s event after accusing Baillie Gifford of “greenwashing”.

The investment management firm rejected Thunberg’s claims that it invests “heavily” in fossil fuels, saying just 2% of its clients’ money was invested in the sector.

Nick Barley, director of the Edinburgh International Book Festival, said the festival would consider the authors’ concerns “carefully” and keep an open mind about how to proceed.

Responding to the letter, Mr Barley said: “We fully acknowledge your concerns about the devastating impact of fossil fuel exploitation on the climate: as individuals and and as a charity we firmly agree.

“For these reasons, we promise to think about your letter carefully. The last thing we want is to let anyone give the impression we are on opposite sides.

“Just as we promise to listen carefully to you, we ask that you allow us some time to consider your comments. We’d also like to share with you the reasons why we have accepted this sponsorship agreement.

“Like all arts organisations in the UK, we wouldn’t have enough funds to operate without private sponsorship. We looked very closely at the work of Baillie Gifford and it seems to us that they are, in fact, investing in companies that are seeking to resolve the crisis.

“Those companies include Orsted, the Danish wind farm specialist.

“Orsted was mandated by the Danish government to keep two coal-fired power stations open until 2024 as a result of Russia’s invasion of Ukraine – and that is the only reason why a small percentage of their income still comes from fossil fuels.

“I hope you will talk with me and my colleagues, and discuss the complexities of this issue with us.”

Edinburgh International Book Festival and Baillie Gifford have been contacted for comment.