The party’s Spring conference in York backed the idea of creating “associate citizenship” of the EU for those British people who want to continue to enjoy benefits such as freedom of movement.
Guy Verhofstadt, who will represent the European Parliament in the Brexit talks, signalled his support for the associate citizenship idea last year.
The measure would involve people paying a free to retain EU citizenship however there is no clear proposal setting out how much it would cost and what it would permit the holder to do,
Critics have suggested the move would disadvantage those who cannot afford to pay the fee.
Lib Dem foreign affairs spokesman Tom Brake said: “This is not an attempt to divide British people into two classes, as suggested by the political pipsqueak [Conservative MP] Andrew Bridgen.
“It is an attempt to offer as many of the benefits of EU citizenship to UK citizens as possible.
“The likes of Bridgen might have dictated the terms of our departure froom the EU but they are not going to dictate our destination.
“Associate citizenship could provide the hundreds of thousands of young people who voted to stay in the EU the opportunities they are going to be deprived of otherwise.”
Delegates at the conference overwhelmingly backed the motion calling for British people to have access to associate EU membership which “provides as many of the rights of full EU citizenship as possible”.