Votes for 16-year-olds in UK elections are all but inevitable, but there is no public demand or obvious advantage to it, a voting expert has said.
A bill currently going through the Senedd would lower the voting age at the 2021 Welsh Assembly election.
Prof Philip Cowley said evidence suggested 16 and 17-year-olds were less likely to vote than older groups.
But the chair of the panel that backed votes at 16 in assembly polls said the move could revitalise democracy.
Sixteen and 17-year-olds voted for the first time in the Scottish independence referendum in 2014 and can now take part in Scottish parliament and local elections.
They can also vote in Guernsey, Jersey and the Isle of Man.
Prof Cowley, from Queen Mary University of London, has written to the Welsh Assembly saying evidence from other countries with a lower minimum voting age suggests overall turnout would drop, because turnout for 16-and 17-year-olds tends to be lower than other groups.
This was unless, he said, money was spent to specifically target the age group, like in the 2014 Scottish Independence referendum when 16-year-olds voted for the first time in the UK.
“If young voters are ready to vote, then we should not need to allocate specific resources to mobilise them,” he told BBC Sunday Politics Wales.
“That we do, indicates that they are not ready.”
He added: “Even some of the things you used to be able to do at the age of 16, say 10 or so years ago, you can no longer do, things like smoking, buying a firework for example, going into a tanning booth.
“All of these have changed recently and if they’ve changed at all, they’ve tend to change upwards towards 18.
“[Votes for 16] is coming. I think you can see with what’s happening in Wales, what’s already happening in Scotland. The pressure will then build up for elsewhere in the UK.
“When it happens, I don’t think any of the advantages that are being claimed for it will manifest themselves but it is probably inevitable.”
Prof Laura McAllister was chair of the expert panel that, as part of its report on how the Senedd could be developed, recommended votes for 16 and 17-year-olds in Welsh Assembly elections.
She said lowering the vote would be a mechanism to revitalise democracy, “particularly if you align that with a programme of proper political education through the curriculum, and in an extra-curricular environment”.
“We know that getting young people involved in the voting process, whilst they’re still in a secure environment, generally living at home, is likely to be more successful than it is at 18 when they’ve either left home to go to university or entering a more turbulent phase of their life in terms of change.”
She said, looking at the evidence from parliamentary and local elections in Scotland, 16 to 18-year-olds voted in larger numbers than 18 to 25-year-olds.
“So that tells you something at least about the potential that there is to engage young people in the political process,” she added.
BBC Sunday Politics Wales is broadcast on BBC One Wales at 11:00 BST on Sunday and is then available on BBC iPlayer.