Gordon Brown says that he "would walk away with regrets about things that you hadn't been able to do" if he was not to continue as prime minister after the next general election.
He also says that the possibility of his party coming in third place in the popular vote "is not something that [he] sees happening" but after "the electorate have made up their mind [he has] got to accept the verdict".
He was speaking to Dermot O'Leary in one of a series of interviews for BBC Three with the three main party leaders as well as the SNP and Plaid Cymru leaders.
Dermot meets... David Cameron
Dermot meets... Nick Clegg
are still available on iPlayer.
BBC Three is also staging a First Time Voters Question Time programme hosted by Dermot O'Leary and you can
apply to be in the audience
in London on Tuesday 4 May.