Jeremy Corbyn said he will have to win over those tempted to vote Tory if he is to have a chance of forming a Labour government.
Speaking in at a debate in Birmingham, Corbyn said Labour would try to win voters over with the policies the party puts forward.
"We win them over on the basis that we can create a society where we do provide decent housing for all, where we do provide real security for all in work," he said.
"But we also, I think, win an election by inspiring our own supporters, inspiring those that have supported other parties, but above all reach out to young people in our society, only 47% of whom voted in the last election to come on board with us and try and create that decent society."
But Corbyn's leadership rival Owen Smith said: "I think we've got to win over two million people who voted Tory a few months ago."
Smith added: "We got nine million, they got 11 million.
"I want a Labour government in order to put into practice my principles and in order to do that we have got to get the best part of two million people who voted Tory to vote for us."
Corbyn and Smith will battle it out during nine official leadership debates between the pair as they battle it out for the party's top job.
The event in Birmingham, moderated by ITV News Political Correspondent Carl Dinnen, was the fourth.