Neil Young has called on fans to boycott Starbucks, citing the coffee chain’s alleged role in a battle over genetically modified food labelling.

Writing on his website, Young accused Starbucks of “hiding behind” an organisation called the Grocery Manufacturers Association (GMA), which, along with three other food companies, is jointly suing the state of Vermont over a new law requiring genetically modified ingredients to be labelled on food products. Although Starbucks is one of the GMA’s many member companies, the corporation is not itself part of the court proceedings.

“I used to line up and get my latte everyday, but yesterday was my last one,” Young said. “Starbucks doesn’t think you have the right to know what’s in your coffee ... [It] is supporting a lawsuit that’s aiming to block a landmark law that requires genetically modified ingredients be labelled. Amazingly, it claims that the law is an assault on corporations’ right to free speech.”

In a statement, Starbucks denied playing any part in the Vermont legal battle and contended that it has yet to take “a position on the issue of GMO labelling”. The company “is not a part of any lawsuit pertaining to GMO labelling nor have we provided funding for any campaign”, the statement continues. “Starbucks is not aligned with [GMO maker] Monsanto to stop food labelling or block Vermont state law.”

Nevertheless, Starbucks did not condemn the GMA’s move. In fact, a representative of the company said of Vermont’s Act 120: “As a company with stores and a product presence in every state, we prefer a national solution [to GMO labelling]”, rather than state-by-state rules.

Still, Young shows no sign of getting back into a queue for his caramel macchiato. As the singer releases Storytone, his 35th studio album, the open letter remains prominent on his website: “Considering that Starbucks has been progressive on LGBT and labour issues in the past, it’s disappointing that it is working with the biggest villain of them all, Monsanto,” he wrote. “Monsanto might not care what we think – but as a public-facing company, Starbucks does.”

In recent years, Young has been commenting on political issues with increasing regularity. He has attacked the automotive industry, lobbied against fracking, and raised money for a Native Canadian group’s legal fight with oil companies. His new record also includes the song Who’s Gonna Stand Up? (And Save the Earth), which he has offered free to climate change activists.

Storytone debuted at No 20 on the UK’s Official Albums Chart.