Sir Tony Blair has urged Labour to hold to the centre ground and avoid “taxing and spending” its way out of economic turmoil.
The former prime minister also credited Sir Keir Starmer with bringing his party back from “the brink of extinction”.
But in an interview with the Financial Times, Sir Tony said Sir Keir would have to contend with a far more challenging situation than the one he faced when he swept to power in 1997.
He added: “If Sir Keir Starmer wins the election, which I think he’s got a good chance of doing, he’ll be the sixth prime minister in eight years.
“That’s a country that’s in a mess. We are not in good shape.”
He said criticism of Sir Keir’s policy offering as too bland was “nonsense” and that Labour should not equate “being radical with just taxing and spending”.
He added: “The Conservative Party has taxed and spent to the point where we’re in an economic crisis.
“The radical agenda today is all about understanding, mastering, harnessing the technological revolution – everything else is secondary to that.”
The political grandee, who led the Labour government of 1997 to 2007, told the newspaper that while he met Sir Keir “reasonably frequently”, he was “his own person” who had shown “agility and determination” in reshaping the party in the wake of Jeremy Corbyn’s leadership.
Sir Keir has been open about seeking the advice of Sir Tony and Gordon Brown on moving into government.