Discussions took place twice, in 1966 and 1967, just before and just after French leader General Charles de Gaulle vetoed Britain's entry to what was then the Common Market, said Sir Trevor Lloyd-Hughes, a Number 10 press secretary during Wilson's administration.
"Wilson was also pretty fed up with the Commonwealth, because the Commonwealth conference in London in September 1966 was attacking him very heavily over his efforts to settle with Ian Smith the Rhodesia question," he told Radio 4's Today programme.
There were no records of the talks with the US leader, which did not get to the stage of studies or formal investigations, he said, adding: "But they were serious talks." He had recently checked his memory with Lady (Marcia) Falkender, who was Wilson's political secretary. "She totally agrees that he was seriously thinking about this." One reason the idea faltered was because the US was keen for Britain to join Europe to restrain De Gaulle's erratic behaviour.
Sir Trevor said he was raising the issue now as a question for the future. If he was still a political journalist, he would be asking whether Tony Blair had a contingency plan if Euroland - the EU countries with a single currency - "nose-dived".
He asked: "Are we going to become a little Switzerland? I'm looking ahead 10, 20 years. Tony Blair is a man, in my book, of the 21st century. He is always looking way ahead."
Dr Piers Ludlow, from the international history department at the London School of Economics, told the Today programme he would be very surprised if the idea were given serious thought today, although it was a "nice bit of whimsy".Reuse content