The former Ukip leader tweeted: “It’s the last thing I’ve ever wanted but I fear it may be forced upon us. 

“We have to be prepared.”

He claimed a second vote would see an even bigger majority for the Leave campaign and silence the “whingeing” of Remainers for a generation. 

But he said it was vital that Brexiteers began organising to see off the challenge from hardline EU supporters such as Tony Blair, Sir Nick Clegg and former Labour minister Lord Adonis.

“It would be naive to allow Remain organisations to build up war chests, get their campaigns going, get their negative messages out while we Leavers continue to be fractured, splintered, not campaigning, not pressurising MPs.  

“The best way to protect our great victory is to be prepared if they come at us again.” 

He said he had tried but failed in recent months to persuade Leave figures to come together. 

“I’m hoping now that by saying I fear a second referendum may be coming we might just get some Leavers together.

“We need to keep fighting for that victory.” 

Stressing that pro-Remain groups were already campaigning round the country, Mr Farage added: “What if they’re organised and we’re not?  

“That would be absolute madness.” 

Earlier yesterday in a TV interview Mr Farage revealed he was on the verge of a change of heart on a second referendum. 

“My mind is actually changing on all this,” he said. 

“What is for certain is that the Cleggs, the Blairs, the Adonises will never give up. 

“They will go on whingeing and whining and moaning all the way through this process.  

“So maybe, just maybe, I’m reaching the point of thinking that we should have a second referendum. 

“I think that if we had a second referendum on EU membership we would kill it off for a generation. 

“The percentage that would vote to leave next time would be very much bigger than it was last time round. 

“And we may just finish the whole thing off. 

“And Blair can disappear off into total obscurity.”  

Downing Street immediately ruled out a re-run of the referendum. 

“As I have said many times, we will not be having a second referendum,” the Prime Minister’s spokesman said. 

And the former Ukip leader appeared to be at odds with his successor last night. 

Henry Bolton, who took over the leadership of Ukip after last year’s general election, said: “Ukip policy on a second referendum remains unchanged. 

“I am convinced that the Leave side would win a second referendum, should one be held, with an even larger majority.  

“Many Remain voters can now see that the campaign led by the then Prime Minister and Chancellor was deliberately misleading. 

“We have also seen greater investment and growth in a number of sectors since the summer of 2016. 

“We are already seeing the benefi ts of leaving the EU. 

“None the less, to hold such a referendum would be to call into question the decisive importance of the largest democratic exercise ever held by this country and the unambiguous mandate the people gave the Government on that day.  

“Such a second referendum would undermine the fabric of our democratic principles and would weaken the clarity and effectiveness of democratic decision. 

“It would be damaging to the nation.” 

But Arron Banks, a former Ukip donor and close ally of Mr Farage, last night called for a second referendum to go ahead. 

“True Brexiteers have been backed into a corner and the only option now is to go back to the polls and let the people shout from the rooftops their support of a true Brexit,” Mr Banks said. 

“Leave would win by a landslide.” 

Remain campaigners also backed the call for a second referendum, claiming a rerun would have a different result from the 52 per cent to 48 per cent in the 2016 poll. 

Lord Adonis said: “Bring it on.”