An Australian man described as a ‘monster’ has been sentenced to 18 years in prison for the murder of an Irish backpacker in Melbourne last year.

Luke James Wentholt will spend at least 15 years behind bars after pleading guilty to killing David Greene and seriously injuring his friend David Byas on August 26th 2012.

Greene from Cabinteely died in hospital in Australia on September 7 last year after he and his friend Byas from Dun Laoghaire were attacked at a boarding house in St Kilda in August 2012.

The court heard how the convicted criminal brutally stomped on the heads of the two Irish friends in an unprovoked attack "like a crazy monster," the Herald Sun reports.

Earlier in the trial the court heard that Wentholt was angry as Greene, 30, was paying too much attention to his girlfriend.

Wentholt's former girlfriend, Shayla Pullen, told the hearing at Melbourne Magistrates' Court she saw him repeatedly stomp on the heads of the two Irish men.

Greene's mother had previously told the court her son was her best friend and "the kindest person you could meet."

"My whole world had turned upside down at the thought of my beautiful Davie never coming back home to me ever again," Catherine Greene said through tears.

"He had made a lot of people happy in his short life.

"I am so proud of you, Davie, and thank you so much for the wonderful 30 years you have given me as a son.

"Love you so much, Davie - this world was never meant for one as beautiful as you."

Judge Terry Forrest sentenced Wentholt to 18 years in prison, 15 of which will be served without the chance of parole.

Delivering his sentence Justice Forrest said, "David Greene's family have lost a much-loved young man.

"Their grief is compounded by the mindless violence that accompanied his death. His death was unprovoked and totally unnecessary."

Greene’s family watched yesterday's sentencing on a live video stream to their homes in Dublin.

Byas has since returned home to Ireland and is expected to make a full recovery.