Lib Dem councillor Paul Elgood is calling for a change in the law to allow people to vote at 16.
He said the low turnout at the General Election had convinced him change was necessary.
Coun Elgood, who leads the Lib Dem group on Brighton and Hove Council, said: "At 16 you can die for your country but you can't elect those who send you to war.
"You can pay tax but can't choose the Government you are paying it to.
"There's something wrong with a system that lets you sign a marriage certificate at 16 but doesn't trust you with a vote."
Liberal Democrats are backing a campaign for votes at 16 run by the Electoral Reform Society.
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