Nigel Farage has announced that he will stand in the European Parliament elections next month for his new Brexit Party.
The former Ukip leader said he would not, after 25 years of "endeavour", watch British politicians "roll us over" - as he warned of a "fightback".
Mr Farage's comments came after Theresa May said the Government would begin "responsible preparations" for the UK to take part in the European Parliament elections on May 23 if her Withdrawal Agreement has not been ratified by then.
He told Sky News: "I'll be leading the Brexit Party into those European elections as it now looks certain they will happen.
"Am I happy about it? No I'm not - actually I've got many other things in my life I'd like to do, I thought we'd won the Brexit battle but I'm not going to after 25 years of endeavour watch British politicians roll us over.
"This is the fightback and they're going to be very surprised by what they get."
Mr Farage also accused the Prime Minister and parliamentarians of trying to "kill Brexit stone dead".
"They have done it by endlessly kicking the can down the road but what they haven't noticed is the growing anger in this country...
"I think Brexit will happen, I think the genie's out the bottle, I just fear there are more battles to fight until we get there."
The prominent Brexiteer led Ukip to a win in the popular vote at the 2014 European elections - but has failed to win a Westminster seat in seven attempts.
He quit Ukip in December, saying there is a "huge space for a Brexit party in British politics, but it won't be filled by Ukip".
The Brexit Party was founded in January by Catherine Blaiklock, reportedly with MrFarage's full support.