McNamara was granted parole on Friday after serving a third of his seven-year sentence for the 1989 rape. He will be released from Kaitoke Prison on January 22.
Shipton's lawyer Bill Nabney would not comment yesterday about the specific grounds for the appeal, but sources close to the case said it related to alleged inconsistencies in the complainant's story.
Other grounds for the appeal included allegations the complainant had made contradictory statements at the 2005 trial and at another trial earlier this year for businessmen Rene Gaustad Mangnus and Paul Grayden Turney.
Mangnus and Turney were found guilty and imprisoned for providing a false affidavit in support of an appeal by Tauranga fireman Warren Hales, who was jailed along with Shipton, McNamara and former police officer Bob Schollum for the 1989 rape.
At that trial a photograph was produced by the defence which they say went to the heart of the complainant's credibility.
The false affidavit by Mangnus and Turney stated that Hales knew the woman and she had approached him at the concert in a friendly manner. The complainant has repeatedly denied ever attending the show.
She could not be reached for comment yesterday, but she told the Parole Board last month that if McNamara was granted parole it would "vindicate him of a crime second only to murder".
She also told TV3 last night that McNamara's release was "grossly unfair".
"It's been 18 years but it may as well have been yesterday, especially when something like this happens," she said.
She was now concerned Shipton and Schollum would be released when they came up for parole next year. "These men are all tarred with the same brush. It's very difficult to sit back and watch them.
"He [McNamara] got out by default. If the Parole Board [who described the complainant as lucid and intelligent] had had their way, I'm sure they would have kept him in there."
Shipton is eligible for parole in May, but a family spokesperson said the expectation was parole would be rejected despite the fact he was a "model prisoner".
The spokesperson said Shipton had accepted he had been found guilty, but still maintained his innocence.
What upset him most was that many people still did not accept the fact he was acquitted on charges of raping Louise Nicholas. "People need to accept that he was found not guilty on those charges," the spokesperson said. "He is doing his time and he is doing it hard.
"[Christmas] ... will be hideous for him because he is a father. He has a daughter and he is missing out on vital years of her life."
In an interview earlier this year with the Herald on Sunday, Shipton acknowledged he had "done things I'm ashamed of" but insisted he had never raped anyone.