In a scathing attack on the UK Government and European Commission, the former Ukip leader attacked the "deeply worrying" failure of European Union exit talks to address border controls after a meeting with Brussels' chief Brexit negotiator.
He claimed that Mr Barnier does not understand at all that immigration fuelled the vote to leave and believes the result was down to the promise of extra cash for the NHS.
But Government sources told the Daily Express that the senior Ukip MEP is just experiencing the devious negotiating tactics used by the European Commission.
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The meeting took place after Mr Barnier had agreed to meet Remainer delegations led by Labour leader Jeremy Corbyn and separately by former Lib Dem deputy prime minister Nick Clegg.
The European Commission's chief negotiator had claimed after the Clegg meeting that his door was open to everybody who wanted to meet him and Mr Farage took up the invitation.
Another meeting will be held on Tuesday with former Ukip MEP Steven Woolfe, now a leading independent Brexiteer, who is bringing a business delegation including Leave Means Leave co-chairman John Longworth.
In a tense meeting in Brussels, Mr Farage also warned that businesses will push for the Government to walk away from talks if the EU fails to make any concessions on financial services.
He said: "What he really didn't understand at all was that open door immigration within the European Union had been an absolute key driver of all of this.
"He really doesn't see that.
“The most disappointing thing, if I am speaking on behalf of the 17.4 million, most of them anyway, is that it's pretty clear that in the talks that have happened so far immigration, frankly, hasn't even been discussed.
"We haven't even begun to talk about how we are going to put some proper controls in place."
Tariff free deal
Mr Farage said it was clear that the Government has not yet discussed border controls with Mr Barnier, which is "deeply worrying for Brexiteers".
The MEP told the Brussels official that if the EU was prepared to offer a tariff free deal on goods but was not cooperative on services "he might be in for a surprise".
Brussels will find a growing number of British businesses may decide "it's best we just leave" under World Trade Organisation rules if the UK is treated badly, he said.
The former leader warned that it would be pointless to spend years negotiating to get a deal on services that he did not think Mr Barnier "wants to give us".
He said it is time for the EU to "give a bit back" on services but while Mr Barnier was "polite", his body language indicated that he does not want to "give too much on that".
Mr Barnier is expected to hold meetings with other prominent leave supporters in the coming days.
Mr Farage said: "At this meeting no cameras were allowed, no photos were to be taken.