Farage: Bid for Brexit has lost momentum after MP killing

His comment came as he was accused by George Osborne of “whipping up division” with a poster showing a column of migrants walking through the European countryside under the slogan Breaking Point, which the Chancellor said was reminiscent of extremist literature produced in the 1930s.

Leading Leave campaigner Michael Gove also distanced himself from the image, saying he “shuddered” when he saw it.

But Mr Farage denied that he was attempting to stoke up hatred, insisting that in fact he had been the “victim” of such a campaign.

Speaking on ITV1’s Peston on Sunday, Mr Farage said he believed that voters who had made up their minds to vote Leave would still turn out on June 23 to do so, but appeared to accept that the drive to win over waverers may have been hit by Mrs Cox’s death after a violent attack outside her constituency surgery on Thursday, which led to a three-day suspension in campaigning.

“I think we have momentum,” said the leading advocate of Brexit. “We did have momentum until this terrible tragedy. It has had an impact on the whole campaign for everybody.

“When you are taking on the establishment, you need to have momentum. I don’t know what’s going to happen over the course of the next three to four days, but (this was) the action of one person with serious mental issues. What we saw was an act of terrorism.”

Speaking to Peston earlier, Mr Osborne said he hoped Mrs Cox’s death would lead to “a less divisive political debate in our country” with “less baseless assertion and inflammatory rhetoric and more reasoned argument and facts”.

He denounced Mr Farage’s poster – released just hours before the attack on Mrs Cox, and already the subject of complaints to the police over alleged racism – as “disgusting and vile”.

Meanwhile, Ukip’s Northern Ireland leader, David McNarry, has said that the referendum is centrally “about self-determination and sovereign identity”.

He said: “Make the referendum your Independence Day. Leaving is the beginning of controlling our destiny.”