A tale of “two teenage dreams” has ended in a nightmare for pop superstar Katy Perry, with one of her companies infringing on the trademark of a Sydney fashion designer.

Katie Jane Taylor (nee Perry) has sold and designed her own line of clothing under her Katie Perry label since 2007, after being inspired by a trip to Italy.

Singer Katheryn Hudson, more popularly known as Katy Perry, initially fought the Australian registration of the Katie Perry brand but later withdrew her opposition and the mark was registered.

Ms Taylor sued Ms Hudson for infringement in the Federal Court in October 2019, more than 10 years after the Ur So Gay singer started selling her own brand of merchandise, including clothing, under her own name.

“This is a tale of two women, two teenage dreams and one name,” Justice Brigitte Markovic wrote in a judgment published on Thursday.

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The judge found Ms Hudson had infringed on Twitter ahead of her 2014 Prism tour in Australia.

However, the judge found the singer did not owe any compensation to the designer because she had used the Katy Perry mark in “good faith”.

Only her firm Kitty Purry is now liable for damages because of the sale of clothing during the tour, at pop-up stores and on the Bravado website.

Justice Markovic rejected further claims the mark was infringed on through clothing sold at Target and Myer and websites such as Amazon and eBay during the Prism tour or ahead of the Witness Tour, which came to Australia in 2018.

A bid by the pop star and her companies to cancel the Katie Perry mark was also dismissed by the Federal Court.

Speaking to AAP, Ms Taylor said she would “have a champagne” to celebrate the win.

“I’m absolutely over the moon,” she said.

“It’s been about standing up for small business, for Australian law and also for justice and truth.”

The court process was a lengthy one for Ms Taylor, compounded by trolling and bullying, including death threats allegedly sent to her and her family by the singer’s fans online.

“It’s been incredibly stressful within the court … and even outside the court to have to deal with intimidation tactics,” she said.

Ms Taylor could not say how much in damages would be awarded at a later hearing, saying she would leave that to the lawyers.

Ms Hudson, through her lawyers, declined to comment.

-AAP