Queen guitarist Brian May has joined a legal challenge in Swansea to try to stop a plan to cull badgers in parts of mid and west Wales.
Animal charity the Badger Trust has applied to the High Court for a judicial review of the proposed cull, aimed at combating bovine TB infection.
The Welsh Assembly Government has said studies indicate a cull could have an impact on infection in cattle.
A farming union said May's involvement was a "cynical publicity stunt."
May has said the cull is based on "bad science" and called it "genocide."
Ministers have said bovine TB is a serious animal health and welfare issue as well as a huge cost to the taxpayer.
The assembly government gave the final go-ahead for the cull, with more frequent testing of cattle, in January.
The Badger Trust began arguing its case earlier at the High Court sitting at the Swansea Civil Justice Centre.
May, 61, sat through a morning of argument by the trust's barrister who questioned the grounds on which the order was granted.
The guitarist then hit out at the planned badger cull during the lunch-time break and claimed the decision was based on bad science.
"This would be genocide. To me countries do not matter. Badgers are not British they belong to the world and they belong to everyone," he said.
He said the cull programme made no more sense than if it could be proved that by killing all ginger-haired people small pox could be eradicated.
"Anyone would think that doing that was insane but that is what we are proposing to do to badgers. Well that's how I feel about it anyway."
The barrister spearheading the charity's legal challenge, David Wolfe, argued insufficient weight had been given to other alternatives to the cull when the assembly government took its decision.
But Dr Christanne Glossop, chief veterinary officer for Wales, has defended the proposed cull.
"We have a bovine TB crisis that we can't ignore and which needs to be dealt with as quickly as possible," she said.
'Millionaire rock star'
"We have spent over £100m in the last 10 years in trying to control it, but it has escalated now to an unsustainable level and threatens cattle farming across Wales."
She added: "Our programme to eradicate bovine TB is a comprehensive package of measures aimed at tackling the disease in both its main sources, cattle and badgers.
"As part of our programme, we are proposing a limited badger cull in one area of west Wales where 42% of cattle farmers have had a TB breakout in the last six years."
High Court Judge Mr Justice Lloyd Jones is scheduled to listen to continued arguments in Swansea for two days.
Meanwhile The Farmers' Union of Wales branded May's decision to attend the judicial review as a "cynical publicity stunt."
Vice president Brian Walters said: "It is completely galling for those who have to live with the misery and financial losses caused by TB to see a millionaire rock star dropping in to talk about the proposed cull when he has no idea of the desperate need to control this disease."