Nigel Farage says he is ready to fight the European elections in May if Brexit is delayed.
The former UKIP leader, who quit his party in December, said he was seeking “the right political vehicle”.
As things stand, the European Parliament is axing most of the UK’s seats, with a small number to be re-allocated to other countries.
The UK can delay Brexit without holding European elections, EU officials have told the Financial Times.
Elections to the European Parliament are due to take place across 27 EU countries between 23 and 26 May 2019, after the UK has left the EU.
The European Commission said it had “not received any UK request” to extend Article 50, the process taking Britain out of the EU on 29 March, and it urged “caution” over suggestions the plans in place for May’s European elections – without UK participation – would have to be changed.
Prime Minister Theresa May has always insisted the UK will leave the EU on 29 March.
But those campaigning for another EU referendum, including several Conservative MPs, the SNP and the Lib Dems, have suggested Article 50 would need to be extended to allow time for a campaign.
Labour leader Jeremy Corbyn has also conceded that he would have to delay Brexit if he won the general election he is trying to force, in order to negotiate a new deal with Brussels.
Mr Farage said he believed the UK should “just leave” the EU without a deal, on World Trade Organization terms, but he did not see “the will” to do so from the prime minister and the government.
Should Brexit be delayed, he said two possible outcomes were that the UK would end up having to contest May’s European elections, and that there could be another referendum on leaving the EU.
He said the Leave Means Leave group, of which he is now vice-chairman, was getting together cross-party support and recruiting business figures to build a broad base of support to fight another referendum campaign.
“We are getting ready, we are building branches and structure all over the country. I hope we never ever have to effectively use the vehicle but we are building it,” he said.
“I know that the Remain side are well-funded, well-organised – they have been campaigning for two years for this second referendum. And I think it would be negligent of those of us on the Leave side not to prepare, not to get ready, in case this happens.”
Mr Farage, who is currently without a party and sits as an independent MEP after quitting UKIP in December added: “I’m finding the right political vehicle to fight those European elections, if they happen.”
He added: “I will make sure that there is a political party there with a list that I can be part of.”
He ruled out attempting to join the Conservatives, in an interview with Sky News, and hinted that he may seek out one of the new parties he says are being registered all the time in the UK.
Mr Farage’s former party took a swipe at him on Twitter after he announced he was seeking a new political home, accusing him of wanting to “split the pro-Brexit vote”.
Individuals have always been able to stand in European elections in the UK, but they stand little chance of success because of the “party list” voting system.
Seats representing England, Scotland and Wales are distributed according to the D’Hondt system, a type of proportional representation.
The nations are divided into 11 electoral regions and parties vying for election submit a list of candidates to the electorate in each region for their approval.
Northern Ireland uses the Single Transferable Vote system, which does not use party lists.
The European Commission suggested any delay to Brexit would not affect the European elections if it did not go beyond July.
A spokesman said: “We have a legally composed European Parliament which requires directly elected MEPs from all member states, at the very latest on the first day of the beginning of the term of the new parliament which is 2 July.
“This is the legal situation and we would prefer as guardians of the treaty to stay with the applicable legal order.
“In any event, any discussions on this remain theoretical because we saw only yesterday that Prime Minister May again ruled out extending Article 50.”