Sixteen-year-olds should be given the vote in every election from 8 June onwards, the Green Party has said.
Molly Scott Cato, the party's candidate for Bristol West, says if 16-year-olds are eligible to pay taxes, leave home, get married and join the armed forces, they should be entitled to vote.
She said a huge majority of 16- and 17-year-olds wanted to remain in the EU but did not have a vote.
At their campaign launch, the Greens also pledged to scrap tuition fees.
Ms Scott Cato, the Greens' MEP for the South West, was outlining the party's election demands in front of Clifton Suspension Bridge in Bristol, flanked by co-leaders Caroline Lucas and Jonathan Bartley.
Ms Lucas also used the platform to call on Labour to commit to a referendum that would ratify the final Brexit deal - while Mr Bartley argued the Greens were "the antidote to UKIP" and its influence on the government.
During the event, Ms Scott Cato said claims that 16-year-olds were not responsible enough to vote were "elitist rubbish" spread by those who feared change.
Similar arguments had been made during campaigns to give women the vote and to bring the voting age down to 18, she said.
"This election is about the future of Britain, and so it's critical that young people have a say in the direction the country takes - that's why we need votes at 16 now.
"At 16, you're eligible to pay taxes, you can leave home, you can get married, you can even join the armed forces.
"If you can do any of these things, you are entitled to vote - you are entitled to have a say in the direction of your country, you're entitled to have your say on the key issues affecting your life," she said.
"The injustice" of last summer's EU referendum had been that "a huge majority of 16- and 17-year-olds wanted to remain in the EU", yet they had been unable to vote, she said, adding only 24% wanted to leave, compared with the 58% of people over 65 who had voted to leave.
'Time to extend the franchise'
"This was a decision which will impact on 16-year-olds for the rest of their lives," she said.
"We're talking about 1.5 million people, and they just had to sit back and watch in horror as older generations made a decision on their behalf - a decision they didn't want, a decision they didn't agree with.
"We cannot shut young people out of their future in this way again.
"The Green Party demands votes at 16 now - not just for this election, not just for some elections, but for every election.
"Sixteen and 17-year-olds are informed, active citizens, and they deserve to take control of their future.
"It's time to extend the franchise."
Ms Scott Cato said the party also believed free education "is a right, not a privilege", and pledged to scrap tuition fees, which were saddling young people "with a mountain of debt they are unable to pay".
She said student debt amounted to £76bn in England, adding: "Little wonder we're seeing a mental health crisis in this generation."