Convicted murderer David Tamihere said claims he brutally murdered two Swedish backpackers and disposed of their bodies are “ludicrous”.

The Weekend Herald reported that a jailhouse informant who claimed Tamihere confessed to murdering Heidi Paakkonen and Sven Urban Hoglin is being sued for perjury.

The private prosecution is being brought by self-styled jailhouse "lawyer" Arthur Taylor, who claims that the informant made direct admissions to him that he had lied at Tamihere's trial.

Tamihere, who has served his time and now lives in West Auckland, told Fairfax he has a letter from a secret witness who admits lying at his trial.

He also rejected the snitch’s claims about what he is supposed to have done to the dead tourists.

"I dumped them at sea, according to him, stole a runabout from a camping ground and run him out to sea... weighted the body and dropped it over the side. I cleaned the boat up and put it back and then did it again with the female.

"It's just ludicrous."

Charging documents lodged with the court set out nine assertions that “Witness C” is alleged to have made on oath or in a sworn affidavit knowing they were untrue.

Tamihere said the witness’ letter admits the man’s evidence was "all false and fabricated by police" and offers to make a statement exonerating him.

The attempted prosecution - it requires a judge's approval to proceed - is supported by Mike Kalaugher, a private researcher and author of the first book about the Marlborough Sounds murders, The Marlborough Mystery, for which Scott Watson was convicted.

Mr Kalaugher has researched the use of jailhouse informants in New Zealand and told the Weekend Herald they pop up in the cases that remain troublesome for the public, such as Teina Pora and Arthur Thomas.

"I view them as a way of verballing defendants."

The jailhouse informant they accuse of perjury in Tamihere's case has name suppression. He is serving a term of life imprisonment for double murder.

David Tamihere was convicted in 1990 of the murders of Heidi Paakkonen and her fiance Sven Urban Hoglin the previous year.

Ms Paakkonen's body has never been found but the discovery of Mr Hoglin's remains near Whangamata conflicted with testimony by the prison informant, who testified that Tamihere had told him he had weighted their bodies and dumped them at sea.

Charges filed against Tamihere claimed he told the informant that he:*Met Ms Paakkonen and Mr Hoglin at a picnic area.

*Assaulted and tied up Mr Hoglin.

*Sexually assaulted both.

*Disposed of Mr Hoglin by beating his head with a lump of wood.

*Had Ms Paakkonen with him when he "almost got sprung" when "a couple" came across them.

*Strangled Ms Paakkonen.

*Gave Mr Hoglin's watch to one of his sons.

Mr Hoglin's body was found with his watch and a pathologist found no evidence of skull fractures or a broken neck.

At the time of the murders, Tamihere was living rough in the Coromandel, on the run after being convicted of sexually assaulting and threatening to kill a woman.

Tamihere, who had a prior conviction for the manslaughter in 1972 of a young Auckland woman, Mary Barcham, is listed as a witness to the perjury suit. He was in prison at the same time as the informant but maintains he made no confessions. He has admitted stealing the couple's car but denies having met them.

He was released on life parole in 2010 after serving 20 years.

The jailhouse informant is currently in prison, having twice been recalled to serve a life sentence for a double murder.

His last recall came after he indecently assaulted a 14-year-old girl on the day of his release.