The top-up would occur in cases where there are “public confidence issues” or a need to protect the public.

Ministers are also considering introducing US-style sentences in which offenders would be given a jail term of, say, from six years to life, where the lower figure would be the minimum term served.Thousands of less-serious offenders would be fined rather than given a community sentence as part of a wider Home Office attempt to stabilise numbers in jails in England and Wales.

A Home Office consultation paper was published yesterday in response to the political and public furore over the case of Craig Sweeney, who can be considered for release after five years of an indeterminate sentence for kidnapping and assaulting a child.

The changes are being proposed just 17 months after the new indeterminate sentences for public protections were introduced as part of the biggest overhaul in sentencing in a decade.

John Reid, the Home Secretary, said: “Courts should be rigorous in applying their powers to protect society against dangerous and violent criminals. That is why we need to strengthen judges’ hands so they have greater discretion to impose even tougher sentences on offenders they believe pose a very serious risk.”

But the consultation paper made clear that the Government is still trying to reduce the number of offenders who are being sent to jail.

It criticises magistrates and judges for not making greater use of community sentences and urges them to show “self-imposed restraint” when considering sentences.

The paper outlines a series of options to giving judges more power when they give indeterminate jail terms for those convicted of violent and sexual offences which do not attract a mandatory life sentence.

Under the plans, offenders given fixed-term sentences who are assessed while in prison as posing a serious risk to the public would no longer be automatically released at the halfway point. A judge would be given the power to order that they remain in jail.

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