Writing on The Huffington Post UK on Wednesday morning, the Ukip leader said it was a "great triumph for the tens of thousands of Ukip members and supporters" that the idea of Britain leaving the EU issue had now been put "on the nation's agenda".
However Farage insisted that rumours of his party's demise were exaggerated and that the prime minister had not stolen Ukip's main selling point.
"As far as Ukip goes, claims that there is no longer a need for us are nonsense. The genie is out of the bottle: the fight for our country's liberty starts today and we are more relevant than ever," he wrote.
"If David Cameron had promised a free and fair In/Out referendum during this parliament I would have cheered him.
"But we haven't been offered that. Cast Iron Dave - who has a track record on denying the people the chance to have their say - will instead ask the public to forget recent history and trust a manifesto pledge.
"It is clear the prime minister has been forced by public opinion to offer a referendum but it is also clear that the renegotiation he speaks of will be little more than lip service.
"EU leaders have been clear in their warnings to the prime minister that there cannot be an a la carte EU and recently proposed changes can be done without a new Treaty. This denies Cameron the negotiating position he is insisting he has.
Farage added: "They might let us catch herrings in the Solent but not much more."
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