Mr Chance said Labor newcomer Roger Cook would be the deputy opposition leader.

Mr Ripper was widely seen as a safe pair of hands to guide the party as it enters its first stint in opposition for seven years.

Mr Chance said it was a unanimous decision to appoint Mr Ripper as the leader.

He said Mr Cook, the member for Kwinana who snuck in to beat independent Carol Adams at the poll, was a prominent member of the ALP and highly regarded.

"It's a sign of the future and I think caucus were enthusiastic about having the opportunity of having someone of Roger's quality who is not actually new to the party," Mr Chance said.

"He has been a member of the party for more than 20 years and he is a former president of the Australian Labor Party.

"But it was a new look and I think it is an indication of how the Opposition will be taking the fight up to the new Government."

In the Upper House, former child protection minister Sue Ellery will lead the Opposition, backed by Kate Doust as deputy.

Mr Chance said the new team marked a fresh start for Labor, after a leadership reshuffle prompted by the state election loss to the Liberals.

Former Labor leader Alan Carpenter resigned at the weekend after accepting responsibility for the election loss.