Tributes have flowed for controversial cartoonist Bill Leak, who has died suddenly, aged 61.

The newspaper he worked for, The Australian, announced the shock death on Friday afternoon.

Leak died in hospital from a suspected heart attack, with one friend saying he had been ‘hounded to his grave’.

The Australian’s editor-in-chief Paul Whittaker wrote Leak was “a giant in his field of cartooning and portraiture and a towering figure for more than two decades”.

He described Leak as “simply irreplaceable”.

“We will miss him dreadfully and our hearts go out to his wife Goong, his stepdaughter Tasha and his sons Johannes and Jasper,” Whittaker said.

Leak’s last public appearance was on Wednesday night at the launch of his book, Trigger Warning.

He won nine Walkley Awards and 19 Stanley Awards for his work.

Leak made headlines throughout his career, but gained worldwide attention for his 2016 cartoon on the role of Indigenous Australians as parents.

The cartoon was published shortly after the ABC uncovered the improper treatment of young Indigenous inmates at the Don Dale Youth Detention Centre in Darwin.

This cartoon caused a weeks long controversy and an AHRC investigation into Leak.

Here is Leak talking about the Australian Human Rights (AHRC) investigation into him over the above cartoon. This was Leak’s last public appearance:

Bill Leak explains the ‘unpalatable truth’ behind the cartoon that caused the Australian Human Rights Commission to go after him. pic.twitter.com/0IrSIgvTMh

— The Bolt Report (@theboltreport) March 8, 2017

Three complaints were made to the AHRC after the cartoon’s publication, however all were dropped after an investigation.

Leak once declared political correctness “a poison that attacks the sense of humour”.

He also underwent brain surgery after being critically injured in a balcony fall in 2008 but had no memory of the accident.

He recalled suspecting a doctor was “having a lend of him” when he woke from a coma.

Peers and PM pay tribute

Prime Minister Malcolm Turnbull – a friend of 30 years – wrote a heartfelt tribute to Leak on Facebook.

Spectator editor Rowan Dean said Leak had been ‘hounded to his grave’.

Dean said a fatwah issued against the cartoonist for poking fun at the prophet Mohammed forced Leak to sell his house and live in a secret location.

“(He was) determined to see the right things done by the right people and he has been hounded to his grave and it is disgusting.”

Herald Sun cartoonist Mark Knight, who had known Leak for more than 30 years, told The New Daily he “was one of those great Australian, larrikin characters”, and his death was the “loss of a major figure” in the Australian political cartoonist family.

“I can’t quite believe it. He was a surprise a minute … He tried to keep the larrikin spirit alive and he did it through his cartoons and he copped a lot of flack for it.”

“When Bill got into trouble over the cartoon on the Aboriginal father not knowing the name of his child, he copped a lot of flack, and copped a lot of flack from other cartoonists in this country who were saying that what he said was outrageous.”

Leak’s Bob Hawke portrait sits in the Members’ Hall at Parliament House.

“I thought that was a great shame and showed a lack of support and a lack of understanding of the freedom of speech, of other cartoonists criticising him for his right to freedom of speech so I think there was a lot of pressure put on Bill by all that and the Human Rights Commission case.”

“He was under a lot of pressure, but I really admired his wonderful ability to pick a fight and to prosecute it in that wonderful larrikin Australian spirit in his cartoons.”

Knight said Leak was always able to be “eloquent” when defending his controversial cartoons.

“He took on radical Islam in Sydney … he was under a lot of pressure. He never took a backward step, he was never defeated and he was always so eloquent in his defence of what he believed in, even if people thought his cartoons were quite vulgar, he was a very eloquent man.”

“These days, it’s hard being a cartoonist in the modern age through political correctness and this social disease called outrage, the outrage industry is huge. The larrikin spirit we used to have in this country is under fire by this generated outrage. It puts pressure on humorists and satirists and cartoonists to still keep the faith.”

– with AAP and reporting by Louise Talbot and Anthony Colangelo