Corbyn made the remarks at a West Midlands rally
The Labour leader told activists the Tories had not realised how popular his message would be, on the eve of the last full day of the election campaign.
Mr Corbyn declared the his party’s socialist manifesto – described by experts as the most left-wing in decades – has proven popular with voters.
In an attempt to woo young voters, the Labour leader threw an event described by attendees as half-music festival, half-campaign.
Pop band Clean Bandit and lefty comedian Steve Coogan warmed up the event for the hopeful Prime Minister.
And the rally, which took place in Birmingham, was broadcast to similar events in five different cities across the UK.
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Addressing the crowd, Mr Corbyn said: “And they thought it would all be over by June 8, well I’ll tell you what – they underestimated us, didn’t they?
“They underestimated us, they underestimated us and the campaign we would mount.
“And do you know what the turning point was? When we produced this…”
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Mr Corbyn then waved his manifesto, which includes tax hikes on the wealthy and plans to renationalise the rail, mail and water industries.
He added: “And do you know what? We are going to carry it out.
“And it does cost, of course. But we live in a country of great riches – we also live in a country of increasing poverty.”
Large crowds of people gathered in Birmingham to hear Mr Corbyn speak
The Labour leader claimed a victory for Labour would “change the political direction of this country”.
He added: “Let us resolve to do things differently. Invest in education, invest in health, invest in housing, invest in jobs. Invest in a future for all of us.
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Abortion is an issue of conscience for the Labour party.
“This election on this program gives us all an opportunity to change the political direction of this country, what kind of world, what kind of society they want to live in.
“Wherever you go, ask people what kind of country, what kind of world, what kind of society they want to live in.”