Roger Federer has issued a cautiously worded response to mounting criticism, including from climate activist Greta Thunberg, over his sponsorship deal with Credit Suisse.

A dozen Swiss activists appeared in court on Tuesday after refusing to pay a fine for playing tennis inside branches of Credit Suisse bank in November 2018, in a stunt intended to underscore Federer’s relationship with the Swiss financial giant, which is closely linked with the fossil fuel industry.

They also held up banners reading: “Credit Suisse is destroying the planet. Roger, do you support them?” Lawyers for the activists, mostly students, said they were appealing the fine of £17,000 (21,600 Swiss francs / $AU32,000) on the basis they were acting as whistleblowers for the climate emergency. Protesters with signs gathered outside the courtroom in Lausanne, and the hashtag #RogerWakeUpNow has been trending on Twitter.

Facebook Twitter Pinterest People demonstrate in support outside the trial of 12 activists who stormed and played tennis inside a Credit Suisse office in November 2018. Photograph: Jean-Christophe Bott/AP

Thunberg was among nearly 700 accounts to retweet a post from climate activist group 350.org Europe. “Since 2016 @CreditSuisse has provided $57 BILLION to companies looking for new fossil fuel deposits – something that is utterly incompatible with #ClimateAction,” the tweet reads. “@RogerFederer do you endorse this? #RogerWakeUpNow.”

350.org Europe (@350Europe) Since 2016 @CreditSuisse has provided $57 BILLION to companies looking for new fossil fuel deposits - something that is utterly incompatible with #ClimateAction @RogerFederer do you endorse this? #RogerWakeUpNow pic.twitter.com/ED1fIvb4Cr

Federer, who is in Melbourne preparing for the Australian Open, responded this weekend via a statement. But the 20-time grand slam champion stopped short of directly addressing his relationship with Credit Suisse. “I take the impacts and threat of climate change very seriously, particularly as my family and I arrive in Australia amidst devastation from the bushfires,” read Federer’s statement, sent to Reuters.

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“As the father of four young children and a fervent supporter of universal education, I have a great deal of respect and admiration for the youth climate movement, and I am grateful to young climate activists for pushing us all to examine our behaviours and act on innovative solutions. We owe it to them and ourselves to listen. I appreciate reminders of my responsibility as a private individual, as an athlete and as an entrepreneur, and I’m committed to using this privileged position to dialogue on important issues with my sponsors.”

Credit Suisse recently stated it is “seeking to align its loan portfolios with the objectives of the Paris Agreement and has recently announced in the context of its global climate strategy that it will no longer invest in new coal-fired power plants”.

Federer will headline a fundraising exhibition at the Rod Laver Arena on Wednesday in aid of bushfire relief, alongside Rafael Nadal, Serena Williams, Nick Kyrgios, Stefanos Tsitsipas, Naomi Osaka and Caroline Wozniacki.