Gerard Batten has dismissed Nigel Farage’s Brexit Party as a “Tory-lite” ego trip as he insisted only UKIP has a “clear policy” for leaving the EU.
Launching its European election campaign in Middlesbrough, the UKIP leader said democracy was under threat if the Brexit vote was not honoured.
UKIP was a “real political party” with members and a rule book, he said.
Its rival, he said, was a “wholly owned subsidiary of one man’s ego” and a “safety valve for disaffected Tories”.
Mr Farage, UKIP’s figurehead for two decades, quit the party after a bitter fallout with Mr Batten last year.
The two parties are now competing against each other in elections to the European Parliament on 23 May.
UKIP won the most votes and seats of any UK party when the polls were last held in 2014 but has been consumed by internal rows since then.
Mr Batten told activists EU membership had been a “cancer at the heart” of British life for more than 40 years, with the transfer of law-making powers “rotting the soul” of the country.
He said Theresa May “never had any intention” of delivering on the 2016 Brexit vote and had made the UK a “laughing stock”.
He promised to campaign across England and Wales to get UKIP candidates elected on a policy of “unconditional and unilateral” withdrawal from the EU.
The UK should leave without a deal and offer to trade with the EU on a tariff-free basis, or under World Trade Organisation rules, with reciprocal rights for each other’s citizens.
Launching a strong personal attack on Mr Farage, he suggested the Brexit Party was a “safety valve for disaffected Conservatives”.
“UKIP is a real political party, that has a constitution, a governing body and a rule book,” he said. “It has members with rights who elect a leader.
“The Brexit Party has no members or structure. It is an autocracy. UKIP has policies and a manifesto. The Brexit Party does not.
“UKIP is a party of ordinary people from all social classes and backgrounds. The Brexit Party is an alternative Tory Party. It is Tory-lite.
“Their light blue colours tell you everything you need to know about it.”
Only three of the 24 UKIP MEPs elected in 2014 have been selected to represent the party again, with the majority having since left the party.
Mr Batten has been criticised for selecting and then defending Carl Benjamin, a candidate in the South West of England who posted a message on Twitter in 2016 saying he “would not even rape” the Labour MP Jess Phillips.
He has described the comments as “satire” and said they should be seen in the context of Mr Benjamin’s self-appointed stance as a freedom of speech campaigner.