Too many older people who voted for Brexit were "driven by nostalgia" for a world where "faces were white," Sir Vince Cable has said.
The Lib Dem leader said the votes of the older generation had "crushed the hopes and aspirations of young people for years to come."
Speaking at his party's spring conference, he said the government's Brexit policy was a "fraud".
The Lib Dems are campaigning for a referendum on the final Brexit deal.
Sir Vince told an audience of Lib Dem activists in Southport: "I've myself been on a journey. I confess that my own initial reaction to the referendum was to think maybe there was little choice but to pursue Brexit.
"I thought, you know, the public had voted to be poorer - well, that was their right.
"What changed my mind was the evidence that Brexit had overwhelmingly been the choice of the older generation.
"75% of under 25s voted to remain. But 70% of over 65s voted for Brexit," he said.
'Very, very white'
The Lib Dem leader went to say too many older voters were driven by "nostalgia for a world where passports were blue, faces were white and the map was coloured imperial pink".
"And it was their votes on one wet day in June which crushed the hopes and aspirations of young people for years to come," he said.
He also took a swipe at his own party's lack of diversity - it has had a lower proportion of non-white MPs and candidates than Labour or the Conservatives in recent years.
"Looking around the auditorium, we are very, very white," he told the party faithful.
"We must prioritise making our party more ethnically diverse."
The former business secretary called the "vision of a Global Britain signing lots of new trade deals" being pursued by his one-time cabinet colleague Theresa May a "fraud".
"Far from opening our arms to the world, we will be tearing up preferential trade deals we already have with 27 countries in the EU and 74 outside it," he said.
"There is no more eloquent testimony to the government's utter naivety about trade, that at a time when the world is descending into trade war, they put more faith in the Wild West warmonger in Washington and the bully of Beijing than they do in our established friends and trade partners in Europe."
Turning to the Labour Party, Sir Vince said that while the party had made a "few tentative steps towards sanity" it was still "strongly committed" to co-operating with the Conservatives to ensure Brexit goes through.
In doing so, he said, Labour leader Jeremy Corbyn is letting down the people he claims to be defending.
"You cannot speak up for the poor and be complicit in making the country poorer," he said.