Tougher sentencing will put pressure on prisons

The jail population in England and Wales could soar towards 95,000 within six years, Whitehall officials forecast yesterday as the Coalition signalled a toughening in its approach to criminal justice policy.

In a defeat for Kenneth Clarke's liberal instincts on sentencing, the Justice Secretary announced automatic jail terms for 16- and 17-year-olds found guilty of knife offences and American-style mandatory life sentences for offenders convicted of a second violent or sexual crime. Just 24 hours earlier he had expressed grave reservations about both policies, but appeared to have been overruled by David Cameron.

After years of increases, the prison population had recently begun to stabilise – and Mr Clarke said last year he believed it could be cut by 3,000. But it will be boosted by up to 1,000 as looters involved in the summer's riots serve tough sentences imposed by courts. The effect on jails is already beginning to be seen, with the prison population rising to a record 87,670 this month.

And according to new projections by the Ministry of Justice (MoJ), the numbers behind bars could rise to a possible high of 94,800 in 2017, a total that would require the construction of several new jails. Mandatory prison sentences for knife crime committed by adults will also increase the pressure on the prison population.

Numbers of teenagers in custody had been falling in recent years, but the MoJ yesterday estimated that the mandatory jail sentence for 16- and 17-year-olds guilty of knife offences could lead to the imprisonment of up to 400 youngsters a year. Although Mr Clarke yesterday predicted the new "two strikes and you're out" life sentences for the most violent offenders would affect only 20 people a year, the proposals marked a distinct change of rhetoric by the Government on criminal justice.

They come months after Mr Cameron vetoed the Justice Secretary's plans to give sentence discounts to offenders pleading guilty at the earliest opportunity. The new populist tone – unlikely to be welcomed by the Coalition's Liberal Democrats – echoes the hardline "prison works" approach to law and order of Michael Howard when he was Home Secretary between 1993 and 1997.

Juliet Lyon, director of the Prison Reform Trust, said: "Too often mandatory penalties take away judicial discretion, threaten the principles of justice and proportionality and swell already overcrowded jails." Des Hudson, the chief executive of the Law Society, which represents solicitors, signalled his alarm over the moves towards mandatory sentences, both for adults and juveniles.

"Judges should be trusted to exercise their discretion when sentencing offenders, taking into account sentencing guidelines and the maximum penalty laid down by Parliament," he said.

The automatic life sentences for the most serious offenders are replacing the previous Government's system of indeterminate sentences for Public Protection (IPPs), under which more than 6,500 offenders have been sent to jail without a fixed date for their release.