A game designer has sparked controversy after his artificial-intelligence-generated art piece won the top spot at a competition in the United States with critics calling the win a threat to human artists everywhere.

Jason M Allen, 39, and his Theatre D’opera Spatial image beat more than a dozen other entries in the “digital arts/digitally-manipulated photography” category at the Colorado State Fair.

The winning artwork was created using the AI tool Midjourney – which turns lines of text into astonishingly realistic graphics. The award came with a $300 cash prize.

AI tools to generate images have been around for years with companies such as Google and OpenAI being notable investors in these text-to-image systems.

“I’m not going to apologise for it … I won and I didn’t break any rules,” Allen, who is from Pueblo, Colorado, told The New York Times newspaper in an interview published on Friday.

However, many have taken to social media to express their anger and despair over the award, arguing it took away from the hard work invested by humans to physically create noteworthy art.

“Jason Allen, you are NOT an artist. You have never used actual tools. Just texts,” one social media user posted on Twitter. “Midjourney can be fun, but it should never be used to cheat other artists.”

Some expressed fear it could endanger their livelihoods, while others said AI-generated art should have its own separate category going forward – something Allen in an interview with the Pueblo Chieftain newspaper also suggested as a way to resolve any future controversy.

“I’m okay with that, there’s no problem with that. But someone had to be first,” Allen was quoted as saying.

According to the Colorado newspaper, the two judges assigned to the category were not aware Allen’s submission was AI generated – but they added it would not have changed their decision as they were looking for “how the art tells a story, how it invokes spirit”.