During an interview with BBC One's Andrew Marr show, he said there had been a “very desperate attempt to talk Ukip down in recent months”, and that some of the polling organisations of using questionable methods to make it look that way.
Last month, the Election Forecast website estimated Ukip would lose half its seats at the General Election on 7 May, and that the party would end up winning just one seat. Others have come up with similar predictions.
“One or two of the pollsters are using voodoo science to try to produce quite low numbers,” he said.
"The fact is, not only are people who say they're going to vote UKIP more likely to go to the polling station next Thursday than the other parties, we're actually going up in the polls."
Farage also criticised Conservative leader David Cameron's “half-hearted” promise for a referendum on EU membership, and described a vote for his party as a “vote for change”.
Visit our General Election poll tracker to see how the polls changed in the build-up to election day.