The president of the European Commission issued a stark warning about the irreversible nature of Brexit today, joining a rising crescendo of concern among European leaders about the ramifications of a Leave vote.
It comes as Leave and Remain made final pitches for voters a day before the historic referendum which commentators have said will go to the wire.
European Commission President Jean-Claude Juncker, said: "The British policymakers and the British voters have to know there will be no kind of any renegotiation," he said, referring to suggestions that the UK could negotiate a Norway-style arrangement with the EU.
"We have concluded a deal with the prime minister, he got the maximum he could receive, we gave the maximum we could give ... So there will be no kind of renegotiation, nor on the agreement we found in February, nor as far as any kind of treaty negotiations are concerned. Out is out."
French President Francois Hollande also urged people to be aware that Brexit would bring "a very serious risk of Britain losing its access to the single market and everything that goes with the European economic area."
But former mayor of London and prominent Brexit campaigner Boris Johnson hit back, saying: "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."