Three of the country's most notorious criminals - two paedophiles and a killer - have teamed up for regular morning walks around a popular public park in Christchurch.

Serial sex offender Lloyd Alexander McIntosh, is considered so dangerous he could soon become the first person in New Zealand to have his strict monitoring extended as a result of a recent law change.

The others, Ivan Andrew Campbell and Nicholas Iain Hawker, both committed crimes that shocked the nation.

David Walker Escorted: Ivan Andrew Campbell (red cap) and Nicholas Iain Hawker (blue and white jersey) on a morning walk through St Albans Park.

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This week Stuff watched as the the trio completed two laps of St Albans Park, in Edgeware.

They were supervised by three staff from a residential centre where it's understood they are living. All three offenders are subject to electronic monitoring.

A source has raised concerns about the walking group - particularly McIntosh, who has to take drugs to control his sex drive. The public should be aware high-risk paedophiles like him are in their midst, the source said.

"He's still just a real threat and a danger to society. He's made no progress in 10 years. When do you stop giving people chances?"

McIntosh's crimes include the rape of a 23-month-old baby and a 6-year-old child.

In 2004, the paedophile was set to be released to live in a rural Canterbury town, but public outrage forced Corrections to house him in a unit on the grounds of Christchurch Men's Prison. The same year he became the first man to be the subject of a 10-year extended supervision order. That is due to expire on March 14.

However, Stuff has learned that Corrections is to apply to have the order extended for up to another 10 years under the Parole (Extended Supervision Orders) Amendment Act passed late last year.

The legislation allows Corrections to apply for an extension of an existing order, without the offender committing new eligible offences. Extended supervision orders are designed to protect the public from high-risk violent and sexual offenders when they have completed their jail terms.

Campbell, a Hells Angels associate, was jailed for 14 years in 2001 after chaining up a teenage boy in a wardrobe and piercing, tattooing and sexually abusing him.

After he was released on parole, he absconded from the Salisbury St Foundation in 2012 with another high-risk resident and was on the run for almost a week before being caught by police in Arthur's Pass.

He is also subject to an extended supervision order, which came into effect in July last year. Before his release, Campbell told a psychologist he was desperate to be monitored because "I do not trust myself outside prison".

Hawker was 18 when he strangled 15-year-old Vanessa Woodman, slit her throat and stabbed her 32 times in the grounds of Wellington's Onslow College in 1997.

At trial, he was found guilty of murder and sentenced to life imprisonment. He was released on parole in 2011, but recalled six months later after evidence of bestiality and child pornography was found on his computer. He was paroled again in January.

Woodman's mother, Leigh, who is the Sensible Sentencing Trust's national victims adviser, was shocked to learn he had been seen walking around a park in the company of two sex offenders.

"They are mixing the worst of the worst and taking them out in . . . public. I think that's incredibly scary.

"If they want to take them out, take them to the back blocks where there's nobody around."

McIntosh, Campbell and Hawker live at a Christchurch-based residential centre for high-risk offenders who are reintegrating into the community.

The centre's director, Lyn Voice, said its residents were taken for walks in several parks across the city. "These guys are supervised and . . . public safety is our priority and will remain so," Voice said.

"People who go to prison in most cases will return to the community. [At the centre] this is done in a safe, structured and managed way that helps the offender make better choices for themselves."

She declined to comment further.