The billionaire businessman has also cancelled a deal costing some 3,000 jobs.
The staunch Remainer, who campaigned against the Leave vote and has since urged parliament to “take a second look” at the referendum, revealed the losses on Good Morning Britain.
“We’re not any worse than anybody else, but I suspect we’ve lost a third of our value,” he said.
He added: “We were about to do a very big deal, we’ve cancelled that deal that would have involved 3,000 jobs.”
Branson, who has also publicly backed a petition calling for a second referendum, added: “When Brexiteers told the public that people were exaggerating that there would be a financial meltdown I think that its been proven that they were not exaggerating.
“We’re heading towards disaster and therefore in business if you realise you made a bad decision you change it. And we’re not saying overrule it, just let the same people who voted have another chance and that’s democratic.”
Branson also warned that Chinese business partners were already pulling investment from the UK after the vote last Friday.
He told the Guardian: “I met with a group of Chinese businessmen yesterday morning who have invested heavily in England and who are now going to stop investing and withdraw investments they’ve already made.”
“I’m afraid that based on misinformation, people voted for Brexit, which is basically voting for a way of shooting themselves in the foot. The last two days has been absolute pandemonium worldwide in the markets, the pound crashing, the stock markets crashing, and we are heading rapidly towards a recession again. It’s just too sad, so so sad.”
As a result of the 51.9% to 48.1% vote, which saw a turnout of 72.2%, the accompanying market crash saw the pound plummet to a low not seen since 1985.
And it hasn’t just affected those in the Remain camp.
Peter Hargreaves, the biggest individual donor to the Leave campaign, has lost more than £400m in a share price meltdown since the result was announced.
Hargreaves, who gave £3.2m to the campaign, has seen the value of his shareholding in the FTSE-100 listed company fall by 24%.