Political strategist Lynton Crosby turned down the chance to help shape Ukip's 'Leave.eu' no campaign, it has been revealed.
Speaking on BBC Radio 4's Today programme millionaire donor Arron Banks said leaders of the campaign had lunch with the strategist and he said no to joining them.
He said: "He's the Prime Minister's advisor so I would be pretty surprised to see if he did join the campaign."
Banks, a main funder to Ukip's 'Leave.eu' campaign, said campaign leaders had since gone to America to find a strategist.
Britain has a 50/50 chance of leaving the European Union, according to Ukip leader Nigel Farage.
Speaking ahead of his party conference speech this afternoon, the eurosceptic politician claimed as many people were likely to vote to leave the EU as to stay and said he would be dedicating his time to campaigning in the in/out referendum.
He said: "I'm not deserting the party but winning the referendum is absolutely key and that's where our energies must go."
Farage, who earlier this month announced Ukip would be launching its own campaign for a No vote in the upcoming referendum, has already said his party will work with any other group that also shares the aim of ensuring the country leaves the EU.
Nigel Farage will launch Ukip's annual conference on Friday by telling activists they must focus on securing Britain's exit from the EU in a planned referendum.
The party leader believes there is a 50/50 chance of Britain voting to leave the EU and is to pledge all his time to campaigning in the in/out referendum.
"I'm not deserting the party but winning the referendum is absolutely key and that's where our energies must go," he will tell the conference in Doncaster.
"Ukip is committed to leaving the EU, and we have always said that we would work with anybody who shared the same aim."
Ukip secured nearly four million votes in May's general election but only claimed one Westminster seat.
Nigel Farage said Ukip's campaign would be separate from two existing No campaigns ahead of the 2017 referendum.Read the full story ›
UKIP have released a joint statement from Nigel Farage and Chris Wells, the Leader of Thanet district Council, in response to the announcement that Manston airport would be used to ease traffic congestion.
UKIP neither wants nor needs the Ramsgate area, including Manston, to become a lorry park.
This is a simplistic and short term approach to the ongoing crisis in Calais and Dover.
UKIP-controlled Thanet District Council is only interested in getting lorries moving so that business can flourish, not simply transferring the parking problem from Dover into the neighbouring districts.
Ukip spokeswoman Suzanne Evans has been 'sacked' after criticising Nigel Farage during a television interview.Read the full story ›
Parade organisers have banned Ukip from taking part to "protect participants" but denied the decision was politically motivated.Read the full story ›
Ukip leader Nigel Farage has criticised the wording of the question that will be asked at the EU referendum.
Because David Cameron "is opting to give the pro-EU side the positive 'Yes'", he said, "suggests strongly that his negotiations are so much fudge".
"He has already decided which way he wants the answer to be given, without a single power repatriated."
The Government has "catastrophically" failed to control immigration, Ukip has said.
After new figures showed net migration to the UK soared to 318,000 in 2014, Nigel Farage, the party's leader, said David Cameron's claim to be "pulling up the drawbridge" was "absurd".
Cameron's claim to be pulling up the drawbridge is absurd http://t.co/WToFDm2Y7E Net migration up again, now 318,000
Ukip's only MP, Douglas Carswell, said Government plans to strip illegal workers of their pay were "mad" and would "persecute a handful of illegal workers".
Ministers cannot control immigration. Yet these supposed "One Nation" leaders introduce rules to persecute a handful of illegal workers. Mad
Steven Woolfe, the party's migration spokesperson added: “Today’s government announcement on illegal migration is a smoke screen to mask today’s appalling immigration statistics.
"In almost every area, net migration, overall UK immigration, EU immigration, non-EU immigration, sham marriages, bogus students, overstayers; the government has failed catastrophically."
The Ukip leader Nigel Farage has responded to resignation of Ukip MEP Patrick O'Flynn from the party's fron bench by saying he accepted it with "sadness".
"Patrick O'Flynn came in person to tell me he had realised that he had made a mistake and, being the honourable man that he is, tendered his resignation as UKIP Economics Spokesman.
"I accepted his resignation with some sadness, not least because he is very able and has been a great asset to the team. He continues to be a committed UKIP member and MEP."