The letter, which is signed by 51 leading figures within young people's organisations, states that firm pledges for young people are necessary in manifestos as the younger generation will be most affected by the outcome of Britain's withdrawal from the European Union.
"As the generation that will live longest with the outcome of Britain's withdrawal from the EU, we ask you to recognise that young people can have a positive impact on the Brexit negotiations and give real legitimacy to the process," the letter states.
"This election offers a huge opportunity to reshape the nation's priorities and restore young people's confidence in our democracy."
The letter, which has been signed by among others Anna Smee, the chief executive of UK Youth, and Jo Hobbs, chief executive of the British Youth Council (BYC), says their groups will work during the campaign to ensure that young people are engaged in the issues and registered to vote.
It adds: "Since the referendum last year, our organisations have worked to engage young people from every part of the UK and from all backgrounds and political persuasions to present a clear plan for what they want from post-Brexit Britain.
"Our national research and consultation has given us a strong and consistent picture of the top issues that matter to young people in post-Brexit Britain.
"We can show you that younger generations are united on the big issues that will shape their future. Now more than ever, their overwhelming demand to be part of the political process must be acted upon."
Others signing the letter include: Youth Access director Barbara Rayment; Oonagh Aitken, the chief executive of Volunteering Matters; Young Minds chief executive Sarah Brennan; and Julie Bentley, Girlguiding's chief executive.
The move follows a call by BYC chair Anna Barker last week to ensure politicians listen to the views of young people during the campaign.