Christopher Beazley was an MEP for the East of England from 1999 to 2009 and for Cornwall and Plymouth from 1984 to 1994.
He said: “As a lifelong, traditional, one-nation, pro-European Conservative I can no longer sit idly by while my former party plunges the country into disaster.
“Successive Tory Party leaders have failed to confront the nationalist, lunatic right-wing fringe.
“As my daughter put it: ‘David Cameron gambled with our future and lost’.
He added: “I salute the Liberal Democrats’ consistent effort and advocacy for Britain’s EU membership and for the urgent necessity of a people’s vote to decide our future - and most importantly for the future generations who have, as yet, never been consulted.”
Christopher has served as a spokesman on constitutional affairs, home affairs and justice as well as culture and education and for regional development.
Jonathan Brown, Parliamentary spokesman for the Chichester Liberal Democrats, said: “Our country cannot continue on its present course. There is a political realignment underway.
“The Lib Dems are a broad church and welcome all prepared to fight for opportunity and prosperity for us and future generations.
“This government treats Parliament and the public with contempt. It wastes millions of taxpayer pounds on contracts for ferry companies with no ships as it diverts billions into pointless preparations for a no-deal Brexit that would devastate our economy and society.”
He added: “We welcome Christopher’s expertise, experience and enthusiasm. We must deal with the inequality and the taking of people for granted that fuels discontent and despair.
“We must stop the chaos in government and focus on fixing Britain. We must have a People’s Vote to give the country the opportunity to reject the shambolic, incompetent divisiveness of this government’s Brexit fantasies, to remain in the European Union and to move on. We demand better.”