The Shadow Chancellor also rejected suggestions that Labour MPs were distancing themselves from the Labour leader, challenging a journalist to reveal his sources for the claim.
With opinion polls giving Theresa May’s Conservatives a significant lead of up to 20 points, Labour high command has acknowledged that the party faces the “fight of our lives”.
But on the campaign trail in Lincoln, Mr McDonnell said: “We’ve got a lot of work to do, we know the polls at the moment; we know what they’re like. To be frank, don’t believe them.”
He went on: “There’s a rumbling, a subterranean rumbling at the moment, where people are saying we want change.
“And I just say this too: this could be a young person’s election because large numbers of young people are registering; for the first time those interested in politics want to have their say. So I believe in these next few weeks, we can do it.”
Later in Derby, the Shadow Chancellor insisted it was not true that Mr Corbyn was unpopular with the electorate, given how popular his policies were.
“This is rubbish that’s being spoken at the moment,” declared the London candidate.
“However, let’s be clear, what we will be putting over is the type of leader Jeremy will be and people will respect him. Honest, decent, principled and strong in those principles.
“He’s different from Theresa May, he’s not boastful in that way, what he does is achieve a consensus and brings people together. That’s the sort of leader we need,” he insisted.
When a journalist said he had spoken to candidates who did not want to be associated with Mr Corbyn, Mr McDonnell replied: “I don’t accept anonymous sources anymore; name a name. Let’s start a new rule for quality journalism: don’t quote anonymous sources.”
He insisted there was “an enthusiasm out there” for Labour. “We’ve got half a million members, the biggest political party in Europe, out there campaigning and Labour MPs right the way across the political spectrum in the Parliamentary Labour Party working together for a Labour government,” he insisted.
Meantime, the Labour frontbencher, following the publication of Labour’s manifesto, released a video challenging Philip Hammond, the Chancellor, to a TV debate.
Noting how the Prime Minister was hiding from a live head-to-head, he said: “So come on Mr Hammond, come and have a debate with me because once we’ve had that debate people will realise just what your government is all about: more austerity stifling our economy; failing to ensure that people in work are properly paid and undermining those people who can’t work as a result of your benefit cuts.”