The party have already trailed key pledges to woo the next generation of voters, including restoring housing benefit for young people, reducing the voting age from 18 to 16, and allowing tenants to use rent payments to buy their own homes.
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.
Leader Tim Farron said voters "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 party's manifesto today, alongside a commitment to protect the state pension triple lock for the next parliament, the Liberal Democrats said they would launch a pension tax review to look at how a flat rate might work.
Lib Dem support nationally has collapsed since the 2010 election when the party won 23 percent of the vote, propelling it into a coalition government with former Conservative Prime Minister David Cameron.
Elsewhere, the party has said it could raise £1bn in taxes by legalising cannabis.
Across the United Kingdom, the manifesto says the Lib Dems would end the 1 per cent cap on pay rises in the public sector, and reinstate housing benefit for people under the age of 21.
"The Liberal Democrats want you to have your choice over your future", he said.More news: Chelsea boss Antonio Conte forced to remain coy over his future
"Many young people would love to buy a home of their own and get on the housing ladder, but they simply haven't got the large deposit they need", Sarah Olney, the party's candidate in Richmond Park told Cosmopolitan.
Priorities for the party's nine MPs will be to protect rights of EU and United Kingdom citizens, including simplifying the citizenship process, and to campaign for continued membership of single market and customs union.
2 Support for continued United Kingdom membership of the single market and customs union and continued freedom of movement after Brexit.
Liberal Democrats say their proposal to extend the "pupil premium", extra funding that goes to schools which teach pupils from disadvantaged backgrounds, would mean Birmingham schools receive an extra £4.1 million. As part of raising the number, and quality of apprenticeships, we will ensure that all the receipts from the Apprenticeship Levy in England are spent on training, aiming to fund a wider range of types of training.
The deadline to be registered to vote in the June 8 general election is on May 22.
The Lib Dems also say they will end the "anomaly" which sees Police Scotland charged Value-Added Tax despite regional forces in England and Wales escaping the charge.
At the heart of the 95 page document is a pledge to raise income tax on all earners by 1p to pay for extra spending on health and social care and a pledge to hold a second European Union referendum.