A former Conservative prime minister has branded Brexit “an act of collective folly” in a bitter attack on the UK’s decision to leave the European Union.

John Major said Britain’s “enemies celebrated and our friends despaired” at the result of the 2016 referendum.

He accused those who campaigned to leave, which included senior Tories like Boris Johnson and Michael Gove, of spreading “misinformation” to persuade voters not to stay in the EU.

“It left our country poorer, weaker and divorced from the richest free trade market that history has ever seen,” Major said.

“National interest was brushed aside by false hopes and promises. False hopes and promises that even a cabinet dominated by frontline Brexit enthusiasts was unable to deliver.”

The former PM, who led the UK between 1990 and 1997, said the damage caused by quitting the EU “has become only too apparent” as he defended the Remain campaign, which was branded “Project Fear” by its opponents.

He said: “The nation saw Project Fear become Project Reality very easily. It’s no consolation that the majority of the public now overwhelmingly recognises that it was misled in their moments of triumph.

“Brexiteers predicted other countries would follow their lead and leave the European Union. None have. All saw only too clearly that Brexit was packed with disadvantages.

“Far from others leaving the European Union, as we meet, nine further nations now wish to join the European Union, which is an apt comment on how the world saw Britain’s decision.”

Major added: “The United Kingdom once revelled, within the memory of everyone present in this room, in being a leading member of the European Union, with half a billion citizens and the undoubted first ally of the United States, the world’s most eminent superpower.

“Today, we know we are neither, and so does the world.”

His comments come as Rachel Reeves prepares to blame the economic impact of Brexit for the need to put up taxes and cut spending in next week’s Budget.

Meanwhile, polling now shows that most Brits believe the UK economy has got worse since the country left the EU.