Neither contender for the Labour leadership could win a General Election with their current agenda, a party councillor for 30 years has said.
Jeremy Corbyn and Owen Smith will take part in the first live debate of the leadership contest on Thursday.
Russell Goodway, the former leader of both South Glamorgan and Cardiff councils, said Labour needed to move back to the centre ground.
But Labour AM Mike Hedges said the centre ground had lost them voters.
Mr Goodway told BBC Radio Wales’ Sunday Supplement programme he did not think he would see another Labour government in his lifetime.
He said: “I think we’ve learned the lesson over the years we win elections by occupying the centre ground of British politics… the centre of gravity has shifted towards the Conservative party and we have to get it back.
“I’m not sure that somebody who prosecutes the same agenda [as Jeremy Corbyn] has any better chance of winning an election and particularly [an agenda] that seems to be committed to promising a second EU referendum.
“It was in our heartlands, in our core voting areas where people voted in their biggest numbers to leave and I think that to suggest we are going to win those people back by promising another referendum is futile.
“[The message] that’s being put forward by Jeremy Corbyn and his supporters is such a narrow message that it’s leaving so many people in the party who say ‘he doesn’t speak for me’.”
‘Do something different’
He said: “We only have to stay out of power as long as we were out of power between ’79 and ’97 for me to be approaching 80 by the time there will be another Labour government.
“If the party were to split, and I really, really hope it does not split, I think the Labour party would disappear in the way the Liberals disappeared.”
Swansea East AM Mr Hedges said he agreed with Mr Goodway’s stance on the EU referendum.
“This idea of having a second referendum, I can think of no better way of annoying and losing the support of that swathe of Labour supporters in what’s traditionally described as our heartlands,” he said.
But he added: “2010 and 2015 – we lost those elections because of the continuation of the Blair/Brown/Milliband centre of the party.
“We lost a huge number of voters at the last election… they’re the people we have to win back by saying ‘we are not all the same, we are going to do something different’.
“This movement to the centre with everybody trying to say exactly the same things, if the centre parties won we would never have had any non-Liberal Democratic government.”
Mr Hedges said he did expect to see another Labour government if the issues of losing seats and voters are addressed.