Convicted child sex offender Dennis Ferguson has been found dead in his inner-Sydney flat.

Police say they were called to the 64-year-old's flat in Surry Hills after a call from the NSW Ambulance Service yesterday afternoon.

A spokesman says initial reports suggest there are no suspicious circumstances surrounding his death.

Ferguson was convicted of kidnapping and assaulting three children from New South Wales in a Brisbane motel in 1987.

Following his release from a Brisbane jail in 2003, he was relocated several times in Queensland and NSW after being run out of his public housing accommodation due to an outcry from the local community.

In 2009, the NSW Government rushed special legislation through Parliament, allowing the relocation of paedophiles in public housing.

It followed a campaign against Ferguson living in Ryde, in Sydney's north-west.

Ferguson also spent time in jail for not telling police he had a job which involved possible contact with children.

Ferguson's former counsellor Dr Wendell Rosevear, who works with both victims and perpetrators of sexual abuse, told ABC News 24 his client was working to address his behaviour.

"He counselled with me very regularly, usually on one or two-weekly basis and then on a needs basis as he moved to different cities," he said.

"He was honest about the dimensions of his own life, both victimisation and perpetration. That honesty is the biggest predictor of someone's resolution.

"Another element that helped him was an accountable circle of safety around him, of people who knew all about him but were willing to support him get his needs met in healthy ways."

Sorry, this video has expired Counsellor says Ferguson was in 'survival mode'

Hetty Johnston, from the child advocacy group Bravehearts, says there will be no tears shed over Ferguson's death.

"It's not like anyone is applauding it - his time has come - and I think children are safer everywhere for it," she said.

"That's the truth of it and I really do doubt that anyone is going to be very sad about his passing, including myself.

"This is a man that was responsible for enormous trauma - terrible offences committed against innocent children - awful, awful offences.

"That's unforgiveable for what he did, so there's no tears and no sadness in his passing."

Ms Johnston said the media coverage of Ferguson's crimes "helped us raise awareness about the dangers that sex offenders pose to children everywhere" but warned against seeing him as a stereotypical paedophile.

"He was easy to dislike, I suppose," she said.

"And people were much happier to think of sex offenders that were somebody else, not their own family members, not their own friends, but this stranger who looks a bit strange and a bit weird.

"These sex offenders don't look like Dennis Ferguson, in fact they look like anybody and everybody, and these offenders are usually much closer to home."

Police say a report will be prepared for the coroner.