A school teacher's conviction for the so-called "lady in the lake" murder of his wife was "unsafe", Court of Appeal judges have heard.

Gordon Park was found guilty of murdering his wife Carol, whose body was found in Coniston Water in the Lake District 21 years after her disappearance in 1976.

Park, who always maintained his innocence, hanged himself in his prison cell on his 66th birthday in January 2010 while serving a life sentence.

A posthumous appeal brought on his behalf by his son, Jeremy Park, was referred to the court by the Criminal Cases Review Commission (CCRC) which investigates possible miscarriages of justice.

CCRC lawyers told the court on Tuesday that failures by prosecution lawyers to share evidence with the defence at Park's 2005 trial casts doubt on the safety of his conviction.

Henry Blaxland QC said the Crown Prosecution Service (CPS) did not disclose evidence about a key witness who claimed the teacher confessed to his wife's murder in prison, which would have undermined his credibility.

He said the CPS also failed to share the opinion of an expert who believed it was unlikely Mrs Park's injuries were caused by her husband's climbing axe - which prosecutors at trial suggested was the murder weapon.

Mr Blaxland said there is also fresh evidence from dental experts that the axe was not used in Mrs Park's murder.

He said: "May I make it plain that it is our submission that, however one looks at it, the material that is now available should lead this court to come to the conclusion that this conviction is not safe.

"This is a case, a circumstantial case, where it is very difficult to tell exactly what it was that influenced the jury in their decision."

Mr Blaxland added that all the information now available lends new relevance to expert geological evidence given at an earlier appeal, which discredited a link between a rock found near the body and Bluestones, the family home.

CPS lawyers contend there was "compelling" evidence against Park and his conviction is therefore safe.

Mrs Park, also a teacher, went missing in Leece, near Barrow-in-Furness, in July 1976 and Park claimed she had gone to live with another man.

But the mother-of-three's body was found by amateur divers in Coniston Water in 1997.

Park was arrested and charged with her murder, and spent two weeks in prison on remand, but the case against him was dropped in 1998 on the grounds there was not enough evidence available.

Detectives later uncovered fresh forensic and geological evidence said to link him to the murder and he was found guilty at Manchester Crown Court in 2005, bringing to an end one of Britain's most notorious unsolved murder investigations.

A challenge by Park against his conviction was rejected by the Court of Appeal in 2008.

Following his death at HMP Garth in Lancashire, his family continued to campaign for his conviction to be overturned and applied to the CCRC.

The appeal, being heard by president of the Queen's Bench Division Dame Victoria Sharp, Mr Justice Sweeney and Mrs Justice May, is due to continue on Wednesday.

The judges are expected to give their ruling at a later date.