A former armed robber who painted a portrait of his barrister that inspired an Australian television series has won the 2015 Achibald Prize.

The Archibald Prize is Australia's most prestigious and often- controversial portrait competition with the winner receiving 100, 000 Australian dollars (74,075 U.S. dollars).

Newcastle artist Nigel Mislom won the 2015 prize on Friday for his portrait of Australian barrister Charles Waterstreet.

The artist was represented by Waterstreet -- a prominent legal identity in Australia -- forming a close bond with the barrister while serving time in jail for armed robbery.

"At the time I was charged with armed robbery and he basically put his hand up and said that he'd help me, that he'd help sort out the mess that I found myself in and that's what he did," Milsom told Australia's national broadcaster on Friday.

Milsom's father knew Waterstreet's parents.

Milsom justified Waterstreet's prominent hands in the oil-on- linen work, saying he wanted to show the barrister reaching out and offering help.

"I've tried to depict his otherworldly-type character," Milsom said. "He's a complex person so I've had to try and exaggerate a lot of his physical features to capture his largeness."

The work, which took three years to paint, was described by the judges as a clear standout.

The Arichibald prize was first awarded in 1921 and is administered by the trustees of the Art Gallery of New South Wales.

For 2015, more than 40 percent of the artists selected as finalists were new to the Archibald.

"The entries in the Archibald Prize this year have been very diverse -- they've covered the whole circle of life," gallery curator Anne Ryan said. "(They ranged) from a young mother with her new baby, right through to some well-loved people in the art world who died this year."