The votes at 16 all-party parliamentary group (APPG) this week published its campaign report, which sets out the arguments for the legal voting age to be lowered from 18.
These include the contradictory benchmarks for coming-of-age, the need to boost political engagement, as well as the fact that Scotland and Wales have already made changes to allow 16-year-olds to vote.
The issue comes with political difficulties: A poll by YouGov published in May 2018, found 45 per cent of people surveyed opposed lowering the age, with 34 per cent in favour, and 21 per cent "unsure".
The government has consistently rejected the calls, with Prime Minister Theresa May ruling it out her 2017 general election campaign, but support has been growing over the last 20 years - including within the Conservative Party.
Labour, the Green Party and the Liberal Democrats have previously said they would lower the voting age.
And according to the APPG report, there are signs public opinion could soften. Opinion has ranged between -40 per cent and -19 per cent against and analysis suggests that those who are unsure "may break slightly in favour".
YouGov's Joe Greenwood said in the report: "This is an issue on which at least a section of the public do not hold staunch opinions and are open to being persuaded in either direction."
The APPG has spent a year considering evidence on the issue, including from young people, politicians and experts.
Introducing the report, APPG chair and Labour MP Danielle Rowley, said: "During this time, young people in society have been making their voices heard.
"They have demonstrated just how much we are losing out by not appropriately recognising the insights held by young people through our electoral system."
Her party colleague and APPG vice chair Vicky Foxcroft added: "It is ridiculous that 16-year-olds pay taxes, can marry and join the army, but aren't allowed to help decide who runs the country that they contribute so much to."
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Since Scotland allowed 16- and 17-year-olds to vote in a 2014 referendum, the arguments against have been "completely undermined", said Conservative APPG member and former Education Secretary Nicky Morgan MP.
In January last year Wales also lowered the voting age for the country's next local authority elections - to be held in May 2022.
"If we think we're a United Kingdom, or we believe that rules should be consistent, then it's a question of when the rest of the country is going to catch up," said Morgan.
Any moves in this direction should come "hand-in-hand with statutory political, civic and democratic education" in the years before pupils turn 16, said Labour's Jim McMahon MP.
APPG treasurer, Conservative MP Peter Bottomley, argues that as the length of a normal parliamentary cycle is five years, a 21-year-old should be given the ability to judge a choice they made at the beginning of the cycle.
"Let us unite in trusting and engaging with our country's future," he urges.
Commenting on the report, Amanda Chetwynd-Cowieson, who is chair of the British Youth Council - the secretariat for the APPG - said: "The government continues to ignore the request for votes at 16 but we know there are no credible arguments against lowering the age when we allow 16- and 17-year-olds the chance to vote in some elections already."
CYP Now has contacted the Cabinet Office for a response.