The peer and former Liberal Dem leader branded Brexiteers as “dispossessed and voiceless” as he compared the rise of Hitler in Nazi Germany in the 1930s to the referendum result.
He made the outrageous claims during an interview on the BBC’s Pienaar’s Politics show.
Speaking alongside Vote Leave and key Brexit campaigner Iain Duncan Smith, Lord Ashdown said: “I’m deep into the 1930s and boy does this age remind me of the 1930s.
“All the things are there, the revolt against the establishment, the retreat from multilateralism to unilateralism.
“The beginning of protectionism, with those who shout loudest getting heard and the small voice of reason doesn’t.”
Despite 17.4m voters opting for Britain to leave the crumbling European Union, the 75-year-old suggested the country was now retreating away from democracy.
“The reason why the 1930s produced such an apocalyptic end was because the progressive centre was fractured, broken and voiceless,” he continued.
“What we heard in the Brexit debate, Trump too for that matter, was that scream of rage from the dispossessed and voiceless.”
Lord Ashdown’s remarks were quickly shot down by Mr Duncan Smith who said the Remain backer was offering a “complete misreading as to what has happened”.
“People who felt left behind have actually said ‘we’re tried of the kind of system that is being imposed on us and we want to change it’,” he said.
“I think this is the real voice of democracy.”
Two unnamed Cabinet ministers told the Daily Mail any attempt to block Brexit could backfire on the upper house.
One said: “The Lords needs to understand that, if they block this, they will be bringing an existential crisis upon themselves.
“Do they really want to do that? The case for major, major reform would become unanswerable.”