UKIP leader Nigel Farage has said his party is not his priority as he dedicates its annual conference to the campaign to leave the EU.
Party members and activists are gathering in Doncaster, with Mr Farage to deliver a speech at noon.
He said there would be a “surprise” coming together of all anti-EU groups in the country in a “show of unity”.
It was also revealed strategist Lynton Crosby’s firm had rejected an offer to help one of the No campaigns.
UKIP, which is committed to Britain withdrawing from the European Union, had launched its own No campaign for the referendum, which the government has pledged to hold by 2018.
Now it is officially joining forces with millionaire party donor Arron Banks, who is behind The Know campaign – their relaunched campaign will be called “Leave.eu”
But BBC political correspondent Robin Brant says it is not the full team they wanted.
“I understand the man who helped get the Conservatives elected – Lynton Crosby – was approached and his firm offered £2m to work for them,” he says.
The Australian was also approached by people on the Yes side, but he turned both down believing it was too early to commit to either ahead of the government’s renegotiation of the UK’s EU membership, he adds.
by Robin Brant, BBC political correspondent
The UKIP leader believes events on the beaches of Greece and the border of Hungary have vindicated his predictions of “biblical” migration to an EU which cannot control who comes in.
He also believes his claim that so-called Islamic State would use the mass movement as cover for exporting terrorists to Europe is something that mainstream politicians are now repeating.
He thinks it has been “proven” that his party was “utterly right” on migration.
Most of all he – and the vast majority of the audience I suspect – will be relieved and very glad that it is him, once again, at the rostrum giving the leader’s speech.
But there will be some in the room, and more beyond, who increasingly worry that Nigel Farage as the prominent face of the campaign to leave the EU could be holding UKIP back from achieving its ultimate aim.
And it is not a good sign when one of your most prominent supporters, and donors, believes the high point has passed and the party could, quite literally, be over in a few years’ time.
The Eurosceptic Business for Britain group said it wished the campaign group “the best of luck in their endeavours” but would not be able to attend the conference “for scheduling reasons”.
UKIP’s annual conference comes after it won a 13% vote share – almost four million votes – in the general election in May, putting it in third place behind the Conservatives and Labour.
However, the increase in support did not result in any more seats in Parliament.
The theme of the opening day of the conference, which will run over the weekend, is the EU and Britain’s place in the world.
It will include sessions that focus on the current difficulties facing the EU and the opportunities open to the UK if it votes to leave.
Mr Farage told the BBC: “Our conference will not be about me, it will not be about UKIP.
“It will be about the fact we’re celebrating we’ve got a national referendum on our membership of the union – something that UKIP has striven for, for over two decades.”
And he indicated there would be a “coming together of all the people in Britain who want to leave the EU”.
“I’ve been told before that the Eurosceptics all hate each other, there are too many egos. Well, we’re going to surprise you at Doncaster with a show of unity that has not been seen before.”
The UKIP leader said winning the referendum and getting Britain’s “freedom and independence” back mattered to him more than anything else.
“UKIP is not my priority at the moment. I might be leader of it but my priority is fighting this national referendum and winning.”
‘Setting the bar’
Mr Farage said the ongoing migrant crisis and the “chaos” in the Eurozone had spurred a feeling among many that it was now “riskier to stay” in the union than to leave.
“So let’s put aside our differences with people in the Labour party who feel as we do, people in the Tory party who feel as we do. Let’s get together, let’s unite. This referendum is now winnable,” he said.
Speaking on BBC Radio 4’s Today programme, UKIP deputy leader Paul Nuttall said the party would offer the “ground troops” for the campaign.
UKIP would be “going hell for leather” in next year’s local elections, he said, but added the party did not want to wait for David Cameron’s attempts to reform the UK’s relationship with the EU to be completed.
“We believe that we should be setting the bar,” he said.
“It’s a bit like a high jumper – we put the bar up and we say to the prime minister ‘attempt to get over that’.”