Melbourne man pleads guilty to the murder of his interior designer partner

The long-term partner of well-known Melbourne interior designer Stuart Rattle has pleaded guilty to his murder.

Michael O'Neill, 47, pleaded guilty to murdering Mr Rattle, his partner of 16 years, and setting fire to his South Yarra apartment.

Mr Rattle's body was found by firefighters at his South Yarra home last December.

O'Neill's barrister Ruth Shann told Melbourne Magistrates Court today her client was in a "fragile state of mind" and had lost 20kg since his arrest.

She applied to have O'Neill's record of interview with police suppressed from the media in court, saying his "intense distress is apparent" in the interview.

She said there was also an absence of an explanation for why O'Neill "spontaneously reacted as he did".

Magistrate Gerard Lethbridge rejected her application.

O'Neill pleaded guilty to murder and arson.

"I'm guilty your honour," O'Neill told the court.

He will face a directions hearing in the Victorian Supreme Court in September.