The present one-year maximum applies to all 15 to 17-year- olds in Prison Service young offender institutions, apart from those convicted of murder, rape and other very serious offences.
The decision was forced on the Home Office by the rushed response of Kenneth Clarke, when he was Home Secretary, to public concern about crime. Mr Clarke promised in March to put persistent young offenders aged 12 to 15 into secure detention centres. Children who committed three or more offences would be given a maximum sentence of two years. The Bill to authorise the centres is due to go before the Commons in the autumn.
But civil servants noticed that the measure would create an absurdity: the maximum sentence for 12-year-olds would be one year longer than for 16-year-olds. A Home Office review is in progress but sources say the anomaly will be resolved by raising the maximum for the older age group.
Ministers have also looked at the minimum age of criminal responsibility in England and Wales - beneath which children cannot be charged. They considered lowering it from 10 to eight, as in Scotland, but the Home Office seems to have rejected the idea.
However, the list of serious crimes carrying long jail sentences for the young may be extended.
Prison campaigners oppose longer sentences. Stephen Shaw, director of the Prison Reform Trust said: 'Doubling the maximum penalty for teenagers who commit minor offences will inevitably lead to more children spending longer behind bars in these benighted institutions. Magistrates are bound to make use of the increased sentencing powers, particularly when the political lead is to follow the ineffective, cruel and pointless policy of locking teenagers up.'
Paul Cavadino, spokesman for the National Association for the Care and Resettlement of Offenders, said that between 70 and 80 per cent of teenagers offend again on release. 'It is very sad that this country is once again drifting into discredited and bankrupt policies,' he said.