Katie Perry, now known as Katie Taylor, filed a lawsuit in 2019 alleging the US popstar ignored the trademark and sold clothing to fans during her concert tours in Australia via retailers and websites in 2014 and 2018.

The Roar singer's company, Kitty Purry, partially infringed the trademark of Taylor's business, which mostly sells clothing online, by promoting products through social media posts, a judge ruled.

Damages are due to be decided at a later date.

Citing Perry's hit Teenage Dream, federal court judge Brigitte Markovic said in her judgement: "This is a tale of two women, two teenage dreams and one name."

Judge Markovic dismissed a bid by the singer to cancel the Katie Perry trademark.

The judgement was made public after court documents were released on Thursday.

'David and Goliath' win for small businesses

Taylor hailed the verdict as a "David and Goliath" win for small businesses.

"Not only have I fought myself, but I fought for small businesses in this country, many of them started by women, who can find themselves up against overseas entities who have much more financial power than we do," she wrote in a blog post.

The legal battle between the two women began in 2008, when Taylor registered the Katie Perry brand in Australia.

The singer initially tried to block the registration and later launched a legal bid to force the designer to cease and forever desist from using the trademark - but later abandoned the move, Taylor said.

She wrote on her blog: "When this all started back in 2009, I had been designing and manufacturing clothes in Australia under the name I was born with, Katie Perry, which I applied to register as a trade mark for my business - a logical next step. I had no knowledge of the singer at the time.

"Imagine my surprise when one of the reactions I received was a letter from lawyers representing the US singer, Katy Perry.

"They stated that I should immediately stop trading under this name, withdraw all my clothes and sign a document drafted by them to say that from then on I will never trade under this name ever again.

"A true case of David vs Goliath! I felt bullied, insulted and surprised."

But Taylor vowed not to give in and instead "decided to fight against this injustice," she wrote.

"I resisted an attack on me and the trademark.

"We established infringement and the cross claim was dismissed."

The mother-of-two said she has been "bullied and trolled" during the case, with her family and friends also suffering abuse.

Taylor added: "This is a win for small business.

"My two young children have witnessed the importance of standing up for their values, no matter how hard it is."

Katy Perry's representatives have been contacted for comment.

The singer previously defeated an appeal in a $2.8m copyright battle after she was accused of plagiarising part of a rap track for her 2013 hit, Dark Horse.

A jury ruled in favour of rapper Flame, real name Marcus Gray, but a federal appeals court decided Perry and her team were not liable to pay the sum, worth about £2.1m, in March last year.

A copyright court case alleging Ed Sheeran ripped off Marvin Gaye's iconic track, Let's Get It On, in his song Thinking Out Loud, began in the US this week.