An Australian fashion designer has been accused of giving “absolutely and utterly” false evidence she had no idea pop star Katy Perry was selling clothes under that name.

Sydney-based designer Katie Jane Taylor – nee Katie Perry – is suing the American singer-songwriter in the Federal Court, arguing that the latter is infringing on her trademark.

The legal dispute is over who can sell clothing branded with the name “Katie/Katy Perry”.

Under fierce cross-examination on Tuesday, Ms Taylor maintained she was unaware in 2009 that Katy Perry was selling merchandise in Australia using her stage name.

But Matthew Darke SC, representing Perry, said Ms Taylor was lying under oath and in her affidavit “to explain the inordinate delay in commencing these proceedings” over a decade later.

He said this was referenced in A Current Affair interview in November 2019 where she said “for the last 10 years I’ve had to watch her infringe on my trademark”.

On January 29, 2009, Ms Taylor posted a YouTube video address to the singer.

“I’m absolutely no threat whatsoever to you. I welcome you to come and visit my studio when you do come here for your concert in August … you’re a girl who has a dream just like myself. I wish you all the success but leave me to carry on my dream,” she says in the online clip.

“Your position was that you were happy for her to use the trademark as she pleased. And you knew full well her dream included merchandising her name on clothes at concerts, because that’s what all music performers do,” Mr Darke said.

Ms Taylor said she believed the US pop star’s dream was to sing, not sell clothing.

“Just like my dream since I was 11 was to have my own fashion label,” she said.

“I suggest you are being absolutely and utterly dishonest with Her Honour,” Mr Darke said.

Ms Taylor denied this.

She did not understand an email referencing the singer as having “established worldwide reputation for her distinctive fashion style and merchandise”, meaning she was selling clothes, she said.

Nor did she read all comments on a Facebook page she created.

One such comment on the “Support for Australian designer Katie Perry” post referenced the musician had sold clothes via her website.

But Ms Taylor said she followed a Facebook etiquette of liking or commenting on posts she had read, so if she hadn’t she likely had not seen it.

Ms Taylor continues to trade under her birth name, which she trademarked for clothing in 2008.

That’s the same year the singer – legally known as Katheryn Elizabeth Hudson – shot to worldwide fame with her hit I Kissed A Girl.

In 2009 Perry’s lawyers sent cease and desist letters to the fashion designer, who then went public with her battle. The women then attempted to negotiate a “co-existence”.

Ms Hudson, whose stage name combines her first name and her mother’s maiden name, is defending the allegation of trademark infringement and has launched a cross-claim to have Ms Taylor’s trademark cancelled.

She has pleaded that she uses the Katy Perry name in good faith and her use on clothing is unlikely to deceive or cause confusion.

The hearing continues.

-AAP