Theresa May is facing cross-party calls to extend the vote to 16 and 17-year-olds in June’s general election.
Green Party co-leader Caroline Lucas said the Prime Minister should make an “urgent change” in the law to allow them to have a say in “their future”.
“If this election is, as the Prime Minister says, about a more secure future for this country, if it is an election of such national significance, we should have an urgent change in the law to give Britain's 1.5m 16 and 17-year-olds a say in what will be very much their future on the 8 June,” she told the House of Commons.
SNP deputy leader Angus Robertson echoed her calls, saying: “I totally agree with the Honorable Lady.”
Withholding the vote from 16 and 17-year-olds was “unsustainable”, he said, adding there needed to be more consistency when the vote is extended.
“As somebody who gave his maiden speech about enfranchising 16 and 17-year-olds, I totally agree with the Honourable Lady. It is again unsustainable that young people have been given the vote for some elections and referenda but should be denied it in others,” he said.
The calls come just a day after the Prime Minister announced plans to hold a snap general election. She had previously insisted she would not seek a vote, Her plans were overhwelming approved by Parliamentary vote.
Ms May told the Commons: "We are determined to bring stability to the United Kingdom for the long term and that's what this election will be about - leadership and stability.”
However Labour leader Jeremy Corbyn said the U-turn showed she could not be trusted to run the country.
"The Prime Minister talks about a strong economy, but the truth is most people are worse off then they were when the Conservatives came to power seven years ago," he said. "The election gives the British people the chance to change direction."