The NSW attorney-general has called for a briefing from prosecutors over the plea deal for Brett Andrew Button, who admitted lesser charges over the June 2023 smash that killed 10 people and injured dozens more.
The 59-year-old was led into custody on Wednesday after facing Newcastle Local Court with a throng of supporters.
He pleaded guilty to 10 counts of dangerous driving causing death, nine of dangerous driving causing grievous bodily harm and 16 of furious driving causing bodily harm.
Prosecutors applied to detain Button after he entered the pleas, a move defence lawyers did not oppose.
He was not required to enter pleas to back-up charges including negligent driving causing death.
Another 25 charges of causing bodily harm by misconduct were withdrawn.
Families of the victims are devastated manslaughter charges have been dropped, an advocate says. (Dean Lewins/AAP PHOTOS)
The withdrawal of the manslaughter charges proved an emotional moment for the victims' families, with Matt Mullen - father of dead passenger Rebecca Mullen - sobbing when his daughter's name was read.
Sophie Wheeler, from the Hunter Victims of Crime Assistance League, said families had been left "devastated" by the prosecution decision.
"It's a very difficult day for the families … the legal system has failed to appropriately acknowledge the seriousness of the offences and it will take time for the families to process," she told AAP.
Several relatives of those killed in the crash earlier told Seven News they felt let down and disrespected due to the prosecution move.
Attorney-General Michael Daley said he would ask the Director of Public Prosecutions for a full briefing on the matter when he faced questions about the plea deal in parliament.
Michael Daley told state parliament no one wanted to see families and victims re-traumatised. (Dan Himbrechts/AAP PHOTOS)
"I was concerned … to see media reports that some of the victim's families were not happy with the way the proceedings have been handled," he said.
"Nobody in this place wants to see family members and victims displeased with or re-traumatised by the criminal justice system."
Button was arrested after losing control of a bus carrying wedding guests from the Wandin Valley Estate to Singleton about 11.30pm on June 11.
He previously apologised for the incident, telling reporters outside court in March he was "devastated by what has occurred" and that he was "truly and deeply sorry".
The Office of the Director of Public Prosecutions has declined to comment on the reason for the manslaughter charges being withdrawn.
The bus rolled onto its side after Button lost control while carrying wedding guests. (Darren Pateman/AAP PHOTOS)
The court heard parties had agreed on the facts of the case but victims' families were yet to see the statement and should be able to review them before the details were made public.
Button has previously been accused of taking the roundabout on Wine Country Drive at Greta too fast while driving in thick fog, allegedly telling some passengers to "fasten your belts" before the fatal crash.
The death toll of 10 was the highest for a road accident since 12 were killed in a bus rollover in Brisbane in 1994.
Button returns to court on May 30 when a date for his sentencing will be fixed.
