.. speaking to The Times, Mandelson said anyone who tried to take Labour back to the era before Blair's election as leader in 1994 would wreck the party's chances of a swift return to power.
Addressing Ed Miliband's criticisms, the peer said: "I think that if he or anyone else wants to create a pre-New Labour future for the party then he and the rest of them will quickly find that that is an electoral cul-de-sac."
He said Lord Kinnock and Lord Hattersley – the former leader and deputy leader, who have both voiced support for Ed Miliband – wanted to "hark back to a previous age".
"We're a political party, not a church, and we require the support of voters actively to embrace us, and if we stop recognising that, then we're going to be taken back into those long years of opposition that served us and the country so ill.
"If you shut the door on New Labour you're effectively slamming the door in the faces of millions of voters who voted for our party."