Jeremy Corbyn has urged Labour to "wipe the slate clean" after he was re-elected as party leader following a bitter campaign which saw him defeat challenger Owen Smith.
Mr Corbyn said both he and Mr Smith were part of the "same Labour family" as he appealed for unity after winning 61.8% of the vote.
He thanked voters in the contest for their "trust and support" after receiving 313,209 of the votes cast, compared with 193,229 for Mr Smith.
Referring to the "passionate and often partisan" contest, Mr Corbyn acknowledged "things are sometimes said in the heat of the debate on all sides which we sometimes later come to regret".
But he added: "I will do everything I can to repay the trust and support, to bring our party together, to make it an engine of progress for our country and the people that depend on the Labour Party to protect their interests, and win power to deliver real change in this country."
Mr Corbyn continued: "We have much more in common than that which divides us.
"As far as I'm concerned, let's wipe that slate clean from today and get on with the work we have got to do as a party together."
Mr Corbyn called on Labour MPs to unite behind his leadership and help build support for "a genuine alternative" to the Conservative Government.
"I have no doubt this party can win the next general election whenever the Prime Minister calls it, and form that next government," he said.
"To do that, we have all got to work together."
Mr Corbyn said he had a responsibility as leader to unite the party at conference, in Parliament and across the country.
But he added: "It is also the responsibility of the whole party - Members of Parliament, councillors, party members and our wonderful supporters across the country - to work together and respect the democratic choice that's been made."
He urged all Labour supporters to join him in taking part in a national day of action next Saturday against Mrs May's plans to expand selection in education and open new grammar schools.
Following a summer-long campaign dogged by allegations of abuse between supporters on opposing sides of the party, Mr Corbyn delivered a promise to tackle intimidation.
"Our party has a duty of care to our members," he said.
"That means intervening to stop personal abuse and abiding by the principles of natural justice in the way we handle it.
"Politics is demeaned and corroded by intimidation and abuse. It is not my way and it is not the Labour way and never will be."
The bruising leadership contest followed a mass walkout from the shadow cabinet and a 172-40 vote of no confidence in Mr Corbyn's leadership by MPs.
Urging the party to come back together, Mr Corbyn quoted from the maiden Commons speech of Labour MP Jo Cox, who died after being shot and stabbed earlier this year.
"A lways remember in our party, we have much more in common than that which divides us," he said.
Mr Corbyn added that Labour had more than tripled in size since its general election defeat last spring to become the largest political party in western Europe, with a "nationwide movement" able to win support for the election of a Labour government.
" Now is the time for all of us to focus every ounce of our energy on exposing and defeating the Tories and the damage they are doing to our country," he said.
"Theresa May's Government isn't a new government - it's David Cameron's government with a new hard-right edge, repackaged with progressive slogans but threatening to take the country backwards and dithering as we face the historic challenges of Brexit."
Responding to the Labour leader's re-election, Conservative Party chairman Sir Patrick McLoughlin said: "Labour are too divided, distracted and incompetent to build a country that works for everyone.
"One hundred and seventy-two Labour MPs don't think Jeremy Corbyn can lead the Labour Party - so how can he lead the country?
"Instead of learning lessons from the past, they have engaged in a bitter power struggle that will continue even after they've picked a leader.
"While Labour row amongst themselves, this Conservative Government will continue to deliver a country that works for everyone, not just the privileged few."