The ex-Downing Street communications chief has been brought in by Ed Miliband to advise on the party's 2015 campaign. But he said the party leader had failed so far to follow up his "one nation" approach with sufficient "hard-hitting policy" and predicted he would fail to win an overall majority.
"I think it will be Lab/Lib coalition," he told the left-leaning Fabian Review.
"I was right in 2010, I knew it was going to be a Tory-Liberal coalition."
Mr Campbell said the Labour pledge to freeze energy bills for 20 months was "a good one-nation policy" but suggested more was required.
"One Nation is not established. It means to the public whatever the public wants it to mean. One Nation Labour worked last year for Ed's speech but it wasn't followed through with hard-hitting policy."
There needed to be a "sustained campaign" behind other attractive initiatives, he suggested: "One on the economy, a couple on public services and one about cultural space".
He said rail re-nationalisation was a policy "people can latch onto, and should be explored further".
Speculation over the possibility of a Lab/Lib deal has been reignited in recent days after shadow chancellor Ed Balls signalled that he could work with Nick Clegg in coalition after the next general election.