Child-sex offenders are eating steak and enjoying picnics, sunbathing and playing tennis at Auckland Prison, say jealous maximum security inmates.

Corrections has confirmed residents of Te Piriti, the therapeutic unit for paedophiles, were treated to a BBQ with their families and friends last November as part of their rehabilitation programme.

The event was to assist with building social relationships and help the men's reintegration, the department said.

Te Piriti is one of the country's two specialist child-sex offender units, which aim to reduce re-offending. Inmates who complete the programme are around four times less likely to offend again.

However, an inmate in the notorious D Block maximum-security wing said the favourable treatment of the paedophiles - who were already unpopular with the general inmate population - had caused anger. "Since Corrections removed the vegetation around their compound, D Block prisoners have had a good view of it," he said in an email.

"These are the country's worst sex offenders, often involving multiple small children and violent rapes. Yet they are unlocked for about 12 hours daily and can sunbathe and play tennis."

On the day of the picnic, the source wrote: "Today they are enjoying a ‘Family Day' barbecue for the men and their families, for which Corrections provides steak - otherwise unknown to prisoners - the best we get is sausage."

He said being "forced to look at their luxury" was like an extra punishment.

The inmate noted child-sex offenders were also allowed to live in "motel-like" units and guards had to knock before entering their cells. In comparison, many high security prisoners were on lock-down for up to 23-hours a day.

"The public would be very surprised to learn the sex offenders are treated with kid gloves. D Block inmates resent the special treatment given to the Sex Offenders Unit inmates because they were supposedly given the same sentence - prison - as the sex offenders."

Prison reformer Peter Williams, QC, said the inmate had a point.

"Years ago it was promised D Block would be abandoned because it was without doubt an absolute disgrace. Alcatraz would be favourable."

Conditions in D Block were also the subject of a recent court case, where inmate Paki Toia alleged inhumane treatment. A judgment is yet to be made.

Society couldn't expect people to live in cages, be treated like animals and come out model citizens, Williams said. "There are pockets where people are well cared for but it's not fair and equal across the board. I do think if we're going to reform people we've got to have better conditions for all prisoners, not just a few."

Auckland Prison manager Tom Sherlock said the Te Piriti family day happened twice a year. Vegetables were provided from the unit's own garden and meat from the prison kitchen. "We understand the importance of visitors in maintaining family and social relationships. Positive support increases a prisoner's chance of successful reintegration into the community when they are released."

The Te Piriti programme runs for nine months. A study showed its graduates had a sexual recidivism rate of 5.47 per cent compared with a general rate of 22 per cent.