The idea has resurfaced as a way of countering disaffection with politics among the young and building on the headway being made by citizenship lessons in schools. Mr Blair has urged his colleagues to “think the unthinkable” as they try to reverse the trend of falling turnout in elections.

Voting at 16 would put Britain on a par with Cuba, Brazil and Nicaragua, among others, but out of step with the rest of Europe. The two ministers charged with looking at ways of involving young people more in politics, Yvette Cooper, minister at the Lord Chancellor’s Department with responsibility for elections, and John Denham, the Minister for Young People at the Home Office, back the idea.

Some pressure groups have long argued that at 16 young people can marry, fight for their country and work and pay taxes, and should be entitled to vote. The new interest has been sparked by concern at the slump in turnout at the last general election coupled with the success of citizenship classes in schools.

One government source said: “When young people are learning about politics and citizenship it would be natural to join that up by allowing them to vote at the end of it, when they reach 16.”

The fresh approach was signalled last month when the Government decided not to kill off a Bill, introduced by the Tory peer Lord Lucas of Crudwell, to lower the voting age to 16. Although ministers think his Bill flawed they let it proceed to encourage debate.

The Electoral Commission begins a review later this month of the case for lowering to 16 the age of voting and of standing for election. Any legislation would come after the next election in a package of changes to electoral law.

Such a move would put Britain out of line with the rest of the European Union and most of the developed world, where voting starts at 18. Iran has, at 15, the world’s lowest voting age, followed by Brazil, Cuba and Nicaragua at 16 and a handful at 17. In more than a dozen African and Asian states, including Japan, the right to vote comes at 20 or 21.

If change went ahead it would further increase pressure on politicians to seek credibility among the young. New ways of voting, such as text messaging, which was tried in a handful of areas in last year’s local elections, would also take on added importance to make elections more youth-friendly.

Much has changed since Ted Heath’s victory in the 1970 general election, the first after the voting age was reduced from 21 to 18, which followed the successful mobilisation of the fogeyish Young Conservatives to get out newly enfranchised voters.

The Commons last debated the subject in 1999 when a Liberal Democrat proposal for votes at 16 was heavily defeated. Since then separate reviews of voting in local authority elections in Scotland and Wales have endorsed similar proposals or called for serious discussion of them.

Last week saw the launch of a Votes at 16 campaign backed by several children’s charities. Voting at 16 is already the policy of the Liberal Democrats, Scottish Nationalists, Plaid Cymru and Green Party.

Right to vote

Bosnia-Herzegovina 16 if employed, otherwise 18

Brazil 16 (compulsory from 18)

Cuba 16

East Timor 17

Indonesia 17

Iran 15

North Korea 17

Nicaragua 16

Seychelles 17

Sudan 17

Yugoslavia 16 if employed, otherwise 18

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