Speaking during the UKIP West Midlands regional conference in Wolverhampton, Mr Farage said David Cameron's claims that he had reformed Europe were 'pretty fraudulent' and that it was his job to make sure that people recognised 'the true picture'.
His appearance came as the Prime Minister announced a referendum on Britain's place in the EU will be held on June 23 following a meeting with his cabinet on Saturday morning.
Mr Cameron said his EU reform deal would give Britain 'special status' within Europe by tackling concerns over migrant benefits and exempting the country from the EU drive for a closer union.
But Mr Farage told the Express & Star at the Dunstall Park event: "Against the standard that he himself set this is not a good deal.
"We had talk of fundamental treaty change. None of that has been achieved. They have given us permission to limit benefits and on top of that we have got a series of vague promises with protocols that they say will be written into future treaties.
"Frankly when I saw the Prime Minister in Downing Street saying that he had reformed Europe I thought that was pretty fraudulent.
"I think he is being wilfully deceitful to try and pretend to people in the way he has. To say we have border controls in this country. Well we don't. We've got an open door to 500 million people.
"Yes we've got controls to those who come from outside the EU. But I just don't think they are giving it straight.
"What I want is change. I want something better. It is up to people like me to give the true picture."
Mr Farage accused the government of failing to realise that immigration would be the most important issue for most people in the referendum, and said ministers had attempted to nullify the debate over the UK's borders.
He said figures quoted by Europol boss Rob Wainwright that up to 5,000 Isis fighters had come into Europe through the Mediterranean over the last 18 months should be of grave concern to everyone.
"Inside the Westminster bubble everyone talks about trade, jobs and all the rest of it," he said. "That is terribly important, but the number one issue is border controls, immigration numbers and security.
"Controlling our borders, the whole immigration question is one that Westminster would rather not discuss. They have tried to kill any debate on it.
"The Labour party view for years was that any conversation on immigration was racist. Those of us who dared to speak out about it would receive a shed load of abuse. We've only just moved beyond that.
"The 'remain' campaign know that unless we leave the EU we cannot control the numbers coming through.
"We will have all the economic debates and they are very important, but what will win or lose this referendum will be the immigration argument, of that I'm absolutely convinced."
Mr Farage said he was convinced the country would 'come together' to make 'the right decision' to pull out of Europe.
"I genuinely think we can win this," he added. "Sometimes you have momentum with you in life.
"I think the EU looks old. It looks tired and out of date. It's not working very well and I think for all those reasons, we can win.
"The 'remain' side are basically saying that if we weren't in it we would suffer terribly. It is a whole series of threats, but I feel that our arguments are much more positive and rational."
Mr Farage also spoke at a public meeting of the Europe of Freedom and Direct Democracy party at the same venue on Saturday night.
He urged the 600-strong crowd to remember that the Prime Minister's deal could still be vetoed by the European Court of Justice. When he said that membership of the EU threatened British values and 'our very civilization', he was met with loud cheers in response.
Meanwhile the UKIP leader laughed off the row over George Galloway's 'surprise guest' appearance at a Brexit campaign rally on Friday night. Controversial former MP Mr Galloway's appearance at the London event prompted a walkout by supporters of Grassroots Out, one of the main groups campaigning against Britain's EU membership.
But Mr Farage said the majority of people who left may have done so as a result of the lengthy duration of the event.