The competition is known for pushing the boundaries of what defines a drawing, once giving first place to a hacked up piece of state housing carpet jumbled over a wire.
But fellow artist Alan MacDonald, who also entered the competition this year, said it was time the competition's name was changed to "The Emperor's New Clothes Design Award".
"Apart from the piece not being original, twice over, it is also not a drawing, anymore that pile of carpet that won previously," he told the Herald.
He pointed to a piece by Colorado artist Joel Swanson, also titled "Forward Slash", which appears similar to Lekner's work, and an earlier piece created in the 60s which was also strikingly similar.
Swanson told the Herald he first created his forward slash piece in 2015 as part of a series of non-alphanumeric typewriter patterns.
There was a "rich history" of artists working with patterns made with typewriters, he said.
Since creating Forward Slash, he has made other works with the same concept, which have been exhibited in various contexts.
"While I have no reason to believe that the similar work in question was created intentionally or maliciously, this situation highlights how important it is for artists and institutions to vet their work and ideas," he said.
In a statement, Lekner said she had not known of the other work until after she won the competition.
"My work was made as an extension of experiments with typewriter that I had been doing over a period of time, during which I was starting to shift from using the typewriter as a writing tool to a drawing tool.
"My work was made in good faith and was my reaction to my experiences and was for me an intimate meditation and mark making experience."
Parkin, the philanthropist and arts patron who funds the competition, said all art was derivative in some way.
"I'm quite satisfied with the integrity or the sincerity of the artist."
Parkin said controversy added "spice" to the art world.
"Nobody can get so angry and upset as an artist that thinks that someone has plagiarised somebody else's work."
He said he took no notice of people calling for the name of the competition to be changed to the Parkin Art Prize instead of the Parkin Drawing Prize.
"If asked to define drawing, I would be interested to know what their definition was.
"We've chosen not to wrap rules around it."
Head judge Charlotte Davy said the judging process for the prize was "rigorous" and involved a panel of experts with a broad understanding of many types of art.
"We are confident that there has been no plagiarism with the prize-winning work – in our view the similarities are coincidental and the artists are each working in a different context with differing concerns," she said.
"The concept of simultaneous invention is well recognised through many fields of endeavour; while both of these artists use the forward slash button on a typewriter to execute their piece, any similarities are coincidental and each work stands on its own merits."
MacDonald, who has entered the competition several times and made it to the final exhibition in previous years, said he had been contacted by numerous artists after making comments about Forward Slash on social media.
Some other artists were advocating for a boycott of the competition, he said.
"The message from the artists is simple: either change the name of the competition to Parkin Art Award or employ only drawing experts, not conceptual artist academics, as judges.
"This nonsense of 'questioning' what drawing is, is pure emperor's new clothes territory."
