Mr Smith has said he will not serve under Mr Corbyn
Jeremy Corbyn has been re-elected as Labour leader, comfortably defeating his challenger Owen Smith.
Mr Corbyn won 61.8% of the total vote, a larger margin of victory than last year.
Mr Corbyn said he was "honoured" to have been elected in a contest that followed months of tension with many Labour MPs.
More than half a million party members, trade unionists and registered supporters voted in the contest.
Mr Corbyn won 313,209 votes, compared with Mr Smith's 193,229.
The BBC's assistant political editor Norman Smith said it was a big win for Mr Corbyn which boosted his mandate". The result raised "serious questions" for Mr Corbyn's critics, he added.
The Labour leader has said he will reach out to his opponents, saying they must now unite to oppose Theresa May's government.
There has been speculation that a number of Labour MPs who resigned from Mr Corbyn's shadow cabinet in June over his leadership could return in an attempt to heal the sharp divisions over the party's future direction.
However, the question of whether members of Mr Corbyn's top team should be elected in the future - and by whom - has yet to be settled.
Mr Corbyn was first elected Labour leader in September 2015, when he beat three other candidates and got 59.5% of the vote.
Turnout was higher this time around, with 77.6% of the 640,500 eligible party members, trade union members and registered supporters confirmed as taking part.
The two-month campaign aroused strong passions on both sides and led to legal disputes over the rules and who was entitled to vote.