Mr Farage, 52, who has had two periods as leader of the Eurosceptic party since 2006, announced he was quitting the post after failing to win a House of Commons seat in the 2015 general election, only to change his mind days later.
But this time he insisted he would not go back on the decision – although he will continue as an MEP and indicated he hoped to play a role in the process of negotiating the UK’s withdrawal from the EU.
He said he would guard against any “appeasement” or “backsliding” by ministers implementing the result of the Brexit referendum. Mr Farage said: “During the referendum campaign, I said I want my country back. What I’m saying today is I want my life back, and it begins right now.”
When questioned about his previous decision to stand down, he said: “I won’t change my mind again, I can promise you.”
After a string of failed attempts to get into the House of Commons, he said standing in 2020 was “not on my bucket list”.
But asked about the prospect of a return to the frontline if there was not a satisfactory Brexit deal by the time of the next general election, he said: “Let’s see where we are in two and a half years time. I don’t need to be leader of Ukip, I can be part of that 2020 campaign if we don’t get what we want.”
Mr Farage claimed that the decision to quit had not been an easy one.
“I do feel a degree of part-ownership of the Ukip brand and the journey we’ve been on,” he said. “Letting go of that is not an easy thing to do but I think right now it’s the right thing to do.”
The new leader will be in place by Ukip’s conference in September but Mr Farage insisted he would keep “very quiet” about his potential successor.
Douglas Carswell, the party’s only MP, has been locked in a bitter feud with Mr Farage but ruled himself out of a leadership bid.
“The chances of me standing to be Ukip leader are somewhere between nil and zero,” he told the BBC’s Daily Politics.
But Ukip’s deputy leader Paul Nuttall indicated he was taking soundings with fellow MEPs and the party’s national executive committee about a bid to replace Mr Farage.
The North West England MEP would boost the party’s chances of taking votes off Labour, something Mr Farage identified as key to Ukip’s future.
Mr Farage said if there was a failure to deliver a Brexit deal that met the promises offered during the campaign then “Ukip’s best days have yet to come” with the prospect of major gains in 2020.
He said the next prime minister should be a Brexit-backer but added: “I’m not going to damn any one of them by offering my support”. He said he would keep up the pressure in Brussels as a member of the European Parliament.
“There will be a strong Ukip voice in that parliament during the negotiations,” he said. “If we see significant backsliding or weakness or, frankly, appeasement from the
British government, we will certainly say so.”