The parents of one-punch victim Thomas Kelly are demanding tougher sentencing laws after the serious assault of a Sydney teenager.

Eighteen-year-old Daniel Christie remains in a critical condition at St Vincent’s Hospital after he was punched in the face on New Year’s Eve.

He was assaulted in almost the same spot 18-year-old Mr Kelly was fatally punched in Kings Cross in July 2012.

Mr Kelly’s parents, Ralph and Kathy, started a petition calling for minimum sentencing laws for manslaughter after Kieran Loveridge was sentenced to four years’ jail for their son’s death.

In a statement posted on change.org, where the petition has gained more than 23,000 signatures, the Kellys called for further changes.

“A single punch,” the statement read.

“Another young man fighting for his life. Another family distraught and torn apart.

“When is this going to end? Our hearts go out to the family of young Daniel Christie.”

Mr and Mrs Kelly have called for alcohol or drugs to be identified as a “mandatory aggravating factor” in sentencing.

They also say a victim’s youth and inability to defend themselves should be considered as aggravating factors in sentencing.

The Kellys have also updated their petition to call for the aggravating factor of conditional liberty be expanded to include a good behaviour bond also, which will tackle “repeat offenders”.

“We have asked the NSW Government to incorporate these three key elements into the [NSW Sentencing] Act,” Mr and Mrs Kelly wrote.

“Importantly these additions would be incorporated within all areas of criminal activity, including domestic violence and sexual assault.”

Mr Christie’s family issued a statement on Thursday saying their lives had been turned upside down.

“We don’t agree with the popular term `king-hit’,” the family said.

“We have heard it referred to as a coward punch, which seems to be more appropriate.”

Mr Christie’s alleged attacker, Shaun McNeil, was refused bail in Parramatta Bail Court on Wednesday.

McNeil, 25, allegedly struck three young men before targeting Mr Christie and his brother, Peter, when the other young men tried to hide behind them.