Victoria's highest court has ruled that tougher sentences are needed in cases where drivers are found guilty of gross negligence causing serious injury.

A landmark decision handed down by the Court of Appeal dismissed appeals in two cases where offenders claimed penalties were too harsh.

One driver was sentenced to four years, while another received a three-and-a-half year jail term.

"The court rejected their contentions that their sentences were manifestly excessive," a summary of the ruling said.

Each offender "drove with a very high degree of negligence, with a blood alcohol reading greatly in excess of the legal limit and at a speed that far exceeded the applicable limit".

"[Their] conduct involved a grave departure from the standard of care required of a driver," the ruling read.

"The victims in each case suffered extensive and profoundly serious injuries."

The ruling of Justices Chris Maxwell, Robert Redlich and Pamela Tate went further and said jail terms for such offences overall should be longer.

"The sentences imposed ... are not commensurate with the objective gravity of the offences, as informed by the degree of negligence involved and the consequences for victims," the 67-page ruling determined.

Recent rulings failed to reflect Parliament: Justices

It said recent rulings had failed to reflect the State Parliament's push for higher penalties introduced in 2008.

The maximum sentence is now 10 years.

The ruling said that the increase "was intended - and expected - to lead to a corresponding increase in the sentences actually imposed".

"As the [cases] show, however, the sentences have remained within a relatively narrow band," the judgment said.

"We consider that sentences of six or seven years [for these cases] would have been well within range, given the seriousness of the offending."