Jeremy Corbyn says he did "everything he could" to get Labour into power and he will not "walk away" until another leader is elected.
The Labour leader said the election, which saw the Conservatives sweep aside his party in its traditional heartlands, was "taken over by Brexit".
Mr Corbyn said he was "obviously very sad" but also had "pride" in the manifesto his party put forward.
Some people within Labour have blamed Mr Corbyn's leadership for the defeat.
Asked whether he was part of the problem, Mr Corbyn said: "I've done everything I could to lead this party… and since I became leader the membership has more than doubled and the party has developed a very serious, radical yes, but serious and fully-costed manifesto".
He added: "Those in Leave areas, in some numbers, voted for Brexit or Conservative candidates which meant that we lost a number of seats and we didn't make the gains that I'd hoped we could have done."