Sixteen and 17-year-olds would be able to vote at the next general election, under government plans to lower the voting age.
Democracy Minister Rushanara Ali told the BBC the "seismic" change would ensure young people's voices were heard.
She confirmed the pledge would be part of a raft of measures introduced through a new Elections Bill.
Other changes include expanding forms of voter ID to include UK-issued bank cards, moving towards automatic voter registration and tightening rules on political donations to protect against foreign interference.
The minimum voting age is already 16 for local council elections in Scotland and Wales, and elections to the Senedd and Scottish Parliament.
However for other elections, including to the UK Parliament, local elections in England and all elections in Northern Ireland, it is 18.
Lowering the voting age to 16 across the UK would be the biggest change to the electorate since it was reduced from 21 to 18 in 1969.
https://www.bbc.co.uk/news/live/c93kkg37n3kt
A pledge to lower the voting age to 16 was included in Labour's election manifesto but it did not feature in last summer's King's Speech, which sets out the government's priorities for the months ahead.
Ali confirmed the government was planning to introduce the change in time for 16 and 17-year-olds to vote at the next general election, which is due to take place by 2029 but could be called earlier than this.
She told the BBC: "At 16, a young person can work, they pay taxes, they can join the Army. So there's no reason why from that age, they shouldn't have a say in who governs our country."
Ali added that the move would ensure politicians took into account the concerns of young people on issues ranging from crime to education, work and housing.
However, Conservative shadow minister Paul Holmes said the government's position was "hopelessly confused".
"Why does this government think a 16-year-old can vote but not be allowed to buy a lottery ticket, an alcoholic drink, marry, or go to war, or even stand in the elections they're voting in?" he asked in the Commons.
Among the other plans set out by the government are expanding the list of accepted ID to vote in Great Britain to UK-issued bank cards, which display the voter's name.
Labour opposed the introduction of voter ID under the Conservatives in 2023 but in its election manifesto the party only promised to "address inconsistencies" in the rules "that prevent legitimate voters from voting", rather than scrapping the policy entirely.
Some 4% of people who did not vote at last year's general election said this was because of voter ID rules, according to the Electoral Commission.
The Conservatives suggested allowing bank cards as voter ID could "undermine the security of the ballot box".
Pressed over whether the security checks of digital banks were robust enough to allow bank cards to be used as a legitimate form of voter ID, Ali told the BBC: "We're going to make sure we take the time to introduce the appropriate changes, and that those changes are done gradually, to make sure that there aren't any risks of abuses or things going wrong."
The government said it would also work towards creating an automated voter registration scheme over the coming years, with safeguards so that people are aware of their registration status and can opt-out if they wish.
Currently people in the UK need to register in order to vote, which can be done online or using a paper form.
The Electoral Commission estimates that nearly eight million people are incorrectly registered or missing from the electoral register entirely, with the issue disproportionately affecting private renters and young people.
In a 2023 report it suggested an automated system could involve organisations like the Passport Office providing Electoral Registration Officers with the names and addresses of people eligible to vote so they can be registered.
The government said its plans would mean individuals would not necessarily need to register to vote and instead those eligible could be directly added to the electoral register through better sharing of data between government agencies.
Exactly how this would work has not been confirmed yet, with the government saying it plans to test different methods.
The National Union of Students described lowering the voting age as "a major victory for young people".
It called on the government to make it as easy as possible for 16 and 17-year-olds to vote by scrapping voter ID laws, implementing automatic voter registration and promoting political literacy in schools and colleges.
Meanwhile, the government said changes to the rules around political donations would help to tackle foreign interference.
Currently political parties can only accept donations from individuals registered on a UK electoral register or UK-registered companies which carry out business in the country.
However, there have been concerns that foreign nationals could get around the rules by donating through a foreign company that is registered in the UK.
The issue came to the forefront at the end of last year,
when it was reported that US billionaire Elon Musk could make a donation to Reform UK through the British arm of his social media company X.
Under the plans, political parties would have to assess companies they receive donations from.
Companies would have to make sufficient income in the UK or Ireland to donate.
The government said its proposals would close loopholes that mean a new company, registered only recently without even a single day of trade, owned by anyone, could still donate to a political party.
The Electoral Commission, which oversees elections and regulates political finance in the UK, would be able to hand out larger fines of up to £500,000 to those who breach the rules.
The Liberal Democrats welcomed votes at 16 as "a no-brainer" but said "ministers must go much further to close the door to foreign oligarchs interfering in British politics".
