The party is proposing a second referendum, “to give the people the final say” at the end of the two-year negotiating process.
As well as extra investment for schools and hospitals the Lib Dems are also committed to a £100bn infrastructure investment to help build 300,000 homes a year.
Speaking ahead of the launch, leader Tim Farron said: “Imagine a brighter future.
“You don’t have to accept Theresa May and Nigel Farage’s extreme version of Brexit that will wreck the future for you, your family, your schools and hospitals.
“In the biggest fight for the future of our country in a generation, Jeremy Corbyn’s Labour has let you down by voting with Theresa May on Brexit – not against her.
“The Liberal Democrats want you to have your choice over your future.
“You should have your say on the Brexit deal in a referendum. And if you don’t like the deal you should be able to reject it and choose to remain in Europe.”
The 95-page manifesto – titled Change Britain’s Future – contains a raft of spending commitments funded through taxation.
It includes plans to introduce a 1p rise on income tax to be ring-fenced to be spent on the NHS, social care services and public health which would raise around £6bn a year.
Under the Lib Dems, NHS tax and payments would be detailed on people’s payslips and by 2020 the NHS and social care budgets would be pooled.
The Liberal Democrats would also invest £6.9bn in schools and colleges over the next Parliament, funded in part with not lowering corporation tax levels.
They would also scrap the planned expansion of grammar schools and repeal the rule all new state-funded schools should be free schools.
Controversially they also plan to legalise cannabis so it can be taxed and sold on the high street – which they estimate would raise £1bn in tax revenues.
The party commits to creating a legal market for the production and sale of the substance in its manifesto, making it one of the first political parties to fight an election on a ticket of relaxing drug laws.
Cannabis would only be sold to people over-18 and sales would be strictly regulated under the new proposals.
The party though will maintain many of its promises from the 2015 campaign, including the triple lock on pensions, low carbon economy and increasing police funding.
But it is its proposition of a second referendum that the party hopes will resonate with voters, particularly the 48% who voted to remain inside the European Union.
However, recent polling from Sky Data shows there has not been a significant shift in support towards the party, with only 61% of supporters who backed them in 2015 doing so again this time.
© 2017, Vale of Glamorgan Broadcasting CIC T/A: Bro Radio & Sky News.