Jeremy Corbyn: Let's wipe that slate clean, from today, and get on with the work we have got to do as a party together. Photo: BBC

He won 61.8% of the vote, a larger margin of victory than last year.

He vowed to bring Labour back together, saying "we have much more in common than divides us", insisting the party could win the next election as the "engine of progress" in the country.

More than half a million party members, trade unionists and registered supporters voted in the contest.

In a result announced on the eve of Labour's party conference in Liverpool, Mr Corbyn won 313,209 votes, compared with Mr Smith's 193,229.

Speaking to the BBC's Laura Kuenssberg after his victory, Mr Corbyn said the debate about who led the party was "now over" and Labour needed to take its message on the economy, education and the NHS to the country.

Asked what steps he would take to reassure critical MPs, he said the return of shadow cabinet elections was "absolutely in the mix" although he declined to rule out the possible deselection of sitting MPs in the run-up to the next election.

"I think you will see a lot of changes over the next few weeks," he said.

"They (MPs) have no need to worry at all because it is all about democracy. We are all democratically accountable to our party and to our constituents. They have no need to worry at all. I am reaching out."

Victory will be sweet - not just because it is a confirmation of his remarkable support among thousands upon thousands of members around the country.

It is Mr Corbyn's second defeat of the Labour establishment, who many of his supporters believe have tried to undermine the leader consistently over the last 12 months.

They talk of a "surge in the purge" as the leadership contest progressed - party officials vetting and checking new supporters who had registered to vote.

There are claims that Labour HQ deliberately threw Corbyn supporters off the voting lists to reduce the size of his victory. Corbyn supporters believe many MPs have done nothing in the past year other than try to damage his leadership and today they will be shown to have failed badly in their attempt to oust him.