British broadcaster Channel 4 says UKIP leader Nigel Farage pulled out of its EU referendum debate tonight.
It is understood he has cited "family reasons."
UKIP apparently offered up their spokesperson on immigration - Stephen Woolf - but the broadcaster declined.
Meanwhile the British Prime Minister David Cameron ended his final day of campaigning in the referendum by declaring "we are stronger" in a reformed European Union, while Boris Johnson has said Brexit would allow Britain to "flourish as never before".
Mr Cameron has been travelling across Britain - appearing with the likes of former British prime minister John Major - to urge people to vote 'Remain.'
As both 'Stronger In' and 'Vote Leave' wound up their respective campaigns ahead of voting beginning at 7.00am on Thursday, two opinion polls suggest the result remains on a knife edge.
In his final public speech before voters have their say, Mr Cameron said figures from across the political spectrum are united in urging the country to vote to stay in.
He said: "We are all saying the same thing - we are stronger, we are better off, we are safer in a reformed European Union."
Mr Cameron urged Britons to think of the word "together" as they head to the polls, telling an audience in Birmingham: "There is no problem we are facing in our world today, facing our country today, that isn't helped by working together."
"How are we going to get that bigger and stronger economy, are we going to do it on our own? No, we are going to do it together with others."
On the 'Leave' side, campaigner Boris Johnson has seized on comments by European Commission President Jean-Claude Juncker about the referendum to press his case for the public to opt for Brexit.
Mr Johnson condemned Mr Juncker as an "unelected tinpot figure", and added: "Who elected Jean-Claude Juncker to run anything in this way? Who put him in charge of us in this way?".
"This gives the game away. If we stay in there is no prospect of any further change."
"This is it, folks. We have been told from the horse's mouth that any hope of further change is absolute illusion."
