Nigel Farage has claimed that Britain has a 50/50 chance of leaving the European Union ahead of the party’s conference, starting in Doncaster today.
And he has warned Ukip that he will devote all his time to campaigning in the in/out referendum.
The eurosceptic party leader insisted he would not “desert” Ukip as its annual conference gets under way at Doncaster Racecourse.
But he said the poll on the UK’s future in the EU would take up all his energy as he described his growing confidence in a so-called Brexit.
Mr Farage said: “I used to think we had 33% chance of winning but now I think it is 50%.”
The Ukip leader insisted the party could hold its head high following the general election and predicted it would do well in next year’s polls in Scotland, Wales and Northern Ireland.
He added: “But that is not where my priorities lie. I am more interested in winning the referendum. I’m not deserting the party but winning the referendum is absolutely key and that’s where our energies must go.”
The conference kicks off with a session on “Europe in crisis” that will focus on migration and calls for borders to be secured.
Mr Farage earlier this month launched an independent Ukip campaign for Brexit amid fears Prime Minister David Cameron will stage a vote next year but has said he will not seek designation for himself or his party as official leaders of the No campaign.
The party leader has pledged to work with other “no” groups in the run up to the vote, which will be held before the end of 2017, and “The Know” group - led by Arron Banks, a major Ukip donor - will appear on the conference stage.
They are expected to announce the creation of a new group called “Leave.EU” that will bring together all the no campaigns under one umberella organisation.
In his keynote speech to activists today Mr Farage will say: “Ukip can be proud of the four million votes cast for it this year. But that was under first past the post.
“Next year there are proportional elections in Scotland, Wales, Northern Ireland and London where Ukip will make significant inroads and build our elected and electoral presence.
“But above all we are looking forward to the referendum we have fought for for so long.
“Ukip is committed to leaving the EU, and we have always said that we would work with anybody who shared the same aim.
“We have invited all those groups and organisations who share that aim, and can provide a platform to take that message out across the country.”
Ukip is returning to Doncaster racecourse one year after its first gathering in the South Yorkshire town was used to announce former Conservative MP Mark Reckless was defecting.
The announcement sparked a by-election in Rochester and Strood that Ukip won but the seat fell back to the Tories at the general election.
Ukip will address its dismal parliamentary showing on Saturday with a session on voting reform that will include speeches from Katie Ghose from the Electoral Reform Society.
Smarting after securing nearly four million votes in May but only claiming one Westminster seat, the conference is likely to be less triumphalist than its pre-election gathering.
In the weeks after the poll, Ukip appeared to plunge into freefall as Mr Farage made good on his promise to quit as leader after failing in his bid to become an MP, only to quickly return to the post.
Weeks of infighting among the most senior members of the party followed, with Patrick O’Flynn quitting his economic brief over comments attacking Mr Farage.
In June Ukip was forced to insist that Suzanne Evans had not been sacked as a spokeswoman despite a leaked internal email ordering press officers to keep her off the airwaves when she was caught up in party feuding.