Tony Blair is to unveil a fundamental overhaul of the criminal justice system next week to safeguard the civil liberties of victims at the expense of offenders. The initiative is designed to restore public confidence in the ability of the courts and the police to tackle crime after a torrid few weeks.

But the promise of further action to "rebalance the criminal justice system" angered a former chief inspector of prisons yesterday, while senior legal figures warned of the dangers of abolishing the sentence discount for those who plead guilty soon after they are arrested.

The former chief inspector of prisons, Lord Ramsbotham, said a period of silence on Mr Blair's part was required when it came to crime and prisons: "I just wish he'd shut up, frankly. One of the problems that there has been recently is announcement after announcement from the prime minister that he's going to do this and that and the other, and more people are going to come in for longer," he told the BBC.

"Unfortunately, all that's doing is crowding the system even more than it is. That doesn't just apply to the Prison Service; it also applies to the probation service," he said, adding it was no use blaming an overwhelmed and under-resourced probation service for not doing what it should.

The prime minister is expected to announce a major drive to ensure that human rights legislation is not used to jeopardise public safety, including possibly new legislation and the appointment of legally qualified "public protection advocates" in the police and the courts to counter the activities of human rights defence lawyers.

It is expected that Mr Blair will go far wider in his crime speech than simply promising legislation and further administrative action to end this week's sentencing row. Changes are already expected in the way the parole board goes about making release decisions for serious offenders and the guidelines which allow courts to give a discount of up to one third on the sentences of offenders who make an early plea of guilty.

The lord chancellor, Lord Falconer, yesterday insisted it was the legal system rather than the judges that was at fault, and also promised to take a detailed look at the way the new sentencing framework introduced under the 2003 Criminal Justice Act was operating. The five-year minimum tariff set for the convicted paedophile Craig Sweeney, whose case sparked this week's sentencing row, was calculated under rules set out for discretionary life sentences that date back to 1967 but were confirmed in the 2003 act.

The number of prisoners in England and Wales reached 77,642 last week, just 158 short of a new record high. Phil Wheatley, director general of the Prison Service, has warned it takes three years to build a new prison and he was just managing within a planned capacity of 80,000.

Kevin Martin, Law Society president, also warned yesterday that ministers should not rush to abolish the one-third discount for early guilty pleas after Lord Falconer confirmed it needed urgent attention. He said these promoted desirable aims in the criminal justice system. "These include avoiding victims of crime having to give evidence unnecessarily, minimising 'cracked trials' because the defendant pleads guilty on the morning of trial, and avoiding delays in cases."

The 2003 act: Falconer's concerns

At the heart of this week's controversy over sentencing has been the 2003 Criminal Justice Act. Lord Falconer said he would take a detailed look at some of its main points. They include:

Early release

Prisoners serving 12 months or more do 50% in custody and 50% on licence in the community and can be recalled to prison if they breach conditions. This replaced a system under which prisoners were released after 75% of their sentence without conditions or supervision.

Dangerous offenders

A new breed of indefinite sentences without a fixed final release date is now used for sexual and violent offenders assessed as posing a danger to the public. Those who have committed offences which carry a maximum sentence of 10 years or more may face either a discretionary life sentence or, if they are less serious, an indeterminate public protection sentence. In both cases the judge will set a minimum period after which the prisoner will be released only if the parole board decides he or she no longer poses a risk to the public.

Mandatory life sentences

These remain the ultimate sanction imposed for murder, but now the judges rather than the home secretary set the tariff - the minimum period that must be served before eligibility for parole. The 2003 act sets out starting points for the tariff, ranging from whole life, 30 years and 15 years, with the minimum term set depending on aggravating or mitigating factors. A mandatory lifer may have his or her first parole hearing three years before the expiry of the tariff but this usually only decides whether the prisoner should be moved to an open prison. The parole board decides on further applications and all mandatory lifers who are released are on a life licence and subject to recall.