People who kill someone with a gun, but are not convicted of murder, will face up to 25 years in prison under a new 'homicide by firearm' offence introduced to State Parliament by the Victorian Government.

Key points: The maximum penalty for manslaughter will be increased by five years to 25 years' jail

The maximum penalty for manslaughter will be increased by five years to 25 years' jail A new offence of homicide by firearm will also carry a maximum penalty of 25 years' jail

A new offence of homicide by firearm will also carry a maximum penalty of 25 years' jail The increased penalties will also apply to industrial manslaughter and child homicide offences

The new laws will also increase the maximum penalty for any manslaughter offence by five years to 25 years.

The changes come in response to concerns about sentences handed to people who have killed someone with a firearm but not been prosecuted for murder.

Attorney-General Jill Hennessy said increasing the maximum sentence gave the court more scope to impose sentences that reflected "a broad range of culpability".

One of the cases that led to the new laws was that of Nelson Lai, 35, who fatally shot his 22-year-old girlfriend Rekiah O'Donnell at his Sunshine home in 2013.

Despite threatening to kill Ms O'Donnell in the months before he shot her, Lai was found not guilty of murder.

Lai was convicted of manslaughter after he told a Victorian Supreme Court jury Ms O'Donnell's death was a tragic accident and he would have never pulled the trigger if he had thought the borrowed gun he was waving around was loaded

He was sentenced to nine years and five months in prison, with a non-parole period of six years and 11 months.

Victim's mother welcomes news law

Ms O'Donnell's mother Kerryn Robertson has been fighting for the introduction of the 'homicide by firearm' offence since her daughter's death.

She said she welcomed the new laws, as long as judges imposed the higher sentences.

"In our case if this law was around, he [Lai] could have got five years extra or even more," she said.

"Just increasing the manslaughter laws from 20 to 25 years doesn't mean they [the offender] will get that, there are still loop holes people use to get away with, like drugs."

Ms Robertson said she would continue advocating for even tougher laws, including the introduction of 'Rekiah's Law', which would mean that anyone who shot and killed someone would be charged with murder.

"We want there to be no excuses," she said. "Whether you are on drugs or you didn't mean it, you should still be charged with murder."

Attorney-General Jill Hennessy said the changes followed years of advocacy from victims. ( ABC News: Andrew Ware )

Tougher penalties to apply in child homicide, industrial manslaughter cases

The new offence will carry a standard sentence of 13 years, with the maximum reserved for the most serious offences.

The increase to manslaughter penalties will also apply to industrial manslaughter and child homicide, including in cases where children are left locked in cars on hot days.

Ms Hennessy said the changes were an election commitment and followed years of advocacy from victims.

"We're increasing the maximum sentence for manslaughter to ensure the range of sentencing appropriately reflects the broad range of culpability we see in these cases,'' Ms Hennessy said.

"By boosting the maximum penalties we acknowledge the seriousness of these offences, and the ongoing trauma inflicted on the family and loved ones of victims."