The prime minister will urge Welsh Labour to “listen” and “take stock” following the party’s historic defeat in May’s Senedd elections.
At a speech at Welsh Labour conference in Llandudno, Conwy, Andy Burnham will call on his party to “do things differently”, ahead of the publication of a review into what went wrong in May.
Welsh Labour leader Ken Skates said the findings were “difficult” and voters felt their support had been taken “for granted”.
Labour had dominated Welsh politics for a century, and until the Senedd election had run the Welsh government since the start of devolution.
The vote made Plaid Cymru the largest party for the first time, allowing Rhun ap Iorwerth to become first minister.
Burnham, who was not prime minister at the time, is expected to acknowledge the scale of the defeat when he addresses party members at Venue Cymru.
The former mayor of Manchester will say: “We have to listen. We have to take stock. And we have to commit to doing things differently.
“But we have to go further than that too. Because, let’s be honest, politicians have always said they’ll listen more.
“This time, we’ve got to do more than talk about giving people a voice. We’ve got to give them real power over the decisions that shape their lives.”
Burnham is expected to repeat his calls for more powers to be devolved to local communities in Wales, last made when he met ap Iorwerth in Glasgow in October.
Under the rules that govern the Senedd, set by Westminster, local government powers rest with Cardiff Bay.
Burnham will say devolution to the Senedd was a “huge step forward” but was “never just about moving power from Westminster to Cardiff”.
“We were always supposed to keep pushing power down and out until it reached every postcode.
“I think that’s the challenge for us today… to make sure Welsh Labour is not just the party that built devolution, but the party that takes it forward once again.”
Prof Anand Menon from polling company Public First will present his review into the party’s election defeat at the conference on Saturday.
Ahead of the review, Skates said: “Its findings are difficult, and we take them seriously. People felt that we had stopped listening, public services were not improving quickly enough and we had taken their support for granted.
“Our task is to earn trust again. We will listen carefully, develop a clear offer for Wales and demonstrate through our actions that we have learned.”
Skates said the Senedd elections “were a pivotal point for Welsh Labour. The results were catastrophic for the party, that was clear for all to see.
“But the reasons for our losses, and there were a multitude of reasons, needed a dispassionate assessment.”
Skates is the Member of the Senedd (MS) for Fflint Wrecsam and was appointed Welsh Labour’s leader in July following May’s Senedd election.