Nigel Farage has admitted he "begged" Vote Leave to let him work with its campaign but was "rebuffed and rejected".

Just a fortnight after the Ukip leader appeared to hold out an olive branch to the other Out group, the bitter rivalry reignited as he attacked it for being on the "back foot".

Read more: Scots frightened to admit UKIP support, says David Coburn

Mr Farage warned that Leave campaigners could only win the June 23 referendum with voices from across the political spectrum.

At a speech in central London, he said: "I have tried very hard over the course of this weekend to say, look, we must let bygones be bygones.

"Whatever has been said in the past is irrelevant, we need to be together and I would love myself and Ukip to work with you on this campaign because we are the four horses when it comes to immigration, when it comes to the impact it has had on this country.

"I'm sorry to say that every time I attempt to work with them I am rebuffed and rejected."

Vote Leave won the designation to be the lead campaign, which comes with significant extra spending limits and rights, over the Leave.EU-backed Grassroots Out (GO) supported by Mr Farage.

It followed a bitter war between the rivals that was branded "fratricidal" by Treasury Select Committee chairman Andrew Tyrie earlier this week.

But the day after the announcement, the Ukip leader appeared to hold out an olive branch, saying Vote Leave was ''now in the right place'' and he was certain it ''will do a good job''.

Mr Farage has since appeared on the campaign stage with Commons leader Chris Grayling but the two groups have failed to join forces.

The party leader said he was "thrilled" that six "big-hitting" Cabinet ministers were campaigning for Vote Leave but the group could not win the referendum alone.

"If it was just Vote Leave I think we might have a problem," he said.

"You cannot win the referendum if you are just seen to be a Conservative group campaigning to leave the European Union."

He added: "That's why I've begged Vote Leave to say look 'I'll work with you, I want to work with you'."

"I believe this campaign is winnable providing the Leave campaign is seen to be a group of people from across the political spectrum."

Mr Farage said the Out movement must highlight concerns about the wave of sex attacks in Germany blamed on migrants as well as fears over terrorism to move the agenda to where the "enemy" is vulnerable.

Voters must also be told that if they vote to stay in the EU they are voting to be part of a bloc which will include Turkey as a full member in the near future.

"If you vote to remain you are voting to go into a political union with Turkey. You are voting to go into a free travel area with 77 million people and rising fast in Turkey," he said.

"I used to worry that we were living in an increasingly German-dominated Europe but from what I can see it might become a Turkish-dominated Europe."

Vote Leave do not have the "credible" voices to campaign on immigration because the Cabinet ministers involved have been part of a Government that has overseen an increase in net migration, he said.

Asked why he was viewed as such a divisive character, Mr Farage said it was because he raised issues that others "brushed under the carpet".

"I'm used to be effectively snubbed by the political establishment in this country," he said.

The party leader said Ukip's only MP, Douglas Carswell, did not give views on immigration such prominence.

"He has a slightly different emphasis," he added.

Cabinet minister Justine Greening urged younger voters to turn out for the referendum to stop the Ukip leader deciding their future.

In a speech to the London Business School, the International Development Secretary said leaving the EU was "a one-way ticket, with no clear destination".

"Why would you let Nigel Farage decide your future?" she said.

"It's time for a new generation to have your say. This isn't about party politics, if that's what's switching you off voting.

"It's about taking care of our country's future - of your future. Your country has never needed you to vote more than it will do on 23rd June 2016."

Ms Greening said Britain played a leading role in responding to humanitarian crises and urged voters to be "internationalist" rather than "isolationist".

She added: "At the very moment our views around the table are most needed and can make the most impact, Britain pulling up the drawbridge doesn't stop the world out there from having these problems. It just makes it a lot harder for us to make sure the global response is a smart one, tackling problems at source."