The moaning ex-Foreign Secretary – who lives in New York – claimed the Brexit process will be “painful” for many British voters.
And he attacked Theresa May by claiming the Prime Minister triggered Article 50, the EU’s withdrawal mechanism, too early.
The Europhile, who quit as MP in 2013 after a failed bid to become Labour leader, said: “My analysis is that this is a national crisis.
“There is an aspect of national humiliation associated with what is going on. The triggering of Article 50 was so monstrously premature.
“We’re sitting on a grenade with the pin pulled out. I don’t see any rainbow at the end of this.
“The truth is that the European Union is a civilising force in international life.
“[Former EU president] Jacques Delors’ great achievement was to make sure that the only kind of Europe was a social Europe.
“That’s why I’m increasingly clear that the only kind of Brexit is a hard Brexit.
“What Brexit means is creating divergence from European standards.
“That process can only be hard, and it will be most painful for many of the people I used to represent.”
Millionaire Mr Miliband then used a bizarre analogy about restaurant food to urge pro-Brexit MPs to change their minds.
He told the Guardian: “It’s a very British thing to think that if you order a meal and then don’t like the look of it, you’ve got to eat it.
“I’ve lived in New York for four years and, frankly, if you order a meal here and it looks a bit rancid, you send it back.
“You don’t grit your teeth and poke at it with your knife and fork.
“New information is coming to light about Brexit every week, from lorry queues in Dover to peace in Northern Ireland.
“We cannot close our eyes to that.”