A lawyer for victims of a Black Saturday bushfire that killed 119 people says he is disappointed a class-action trial will be delayed because a new courtroom won't be finished on time.
Victoria's largest civil court case, over the Kilmore East fire, was to have started on January 29 next year but now won't begin until March 4.
Victorian Supreme Court Justice Jack Forrest on Friday said while work has commenced on the new courtroom, it will not be ready in time.
He said inquiries had been made about temporarily using a court in the Federal Court but it was not available and no other suitable venue could be found.
Attorney-General Robert Clark had announced earlier this month that the new, bigger courtroom, which is located in the William Cooper Justice Centre in William Street in central Melbourne, was being refurbished and was due for completion in January, in time for the start of the Kilmore East trial.
A lawyer for the victims, Rory Walsh from Maurice Blackburn, expressed disappointment at the delay.
"Our clients have been waiting for their day in court for nearly four years, despite the trial date being fixed over a year ago in a proceeding to which the state itself is a party," he said in a statement.
"We are now told that our clients will have to wait a further five weeks until March 4 - we are disappointed that this has been allowed to occur."
A spokesman for Mr Clark said the "project team considers that a functional courtroom could still be made available for the scheduled trial start date", but the court had concluded the date should be moved to allow further works to be completed.
The spokesman said the summer shutdown in the building industry would have a greater impact on the building than original anticipated.
Shadow Attorney-General Martin Pakula said Mr Clark must take responsibility for the delay after he gave an assurance that the trial would commence on time.
He said bushfire victims "have become the face of the Baillieu government's tardiness in the state's justice system".
SP AusNet has vowed to "vigorously defend" the class action, which centres on claims relating to the inspection and maintenance of its assets.
The trial is expected to run for six months.
The February 2009 bushfire killed 119 people and destroyed more than 1000 homes.
The delay comes after a statement from Chief Justice Marilyn Warren that Victoria's highest court is in dire need of modernisation to meet the demands of big trials and to be fair to victims.