Some murderers could serve less than 10 years in prison under guidelines unveiled by the Lord Chief Justice of England and Wales, Lord Woolf.
Lord Woolf has endured a torrid time in the press
But it would only be in extraordinary circumstances - for example, if they had given themselves up before their crime had even been detected, he said.
People admitting serious offences at the first opportunity could be entitled to a 33% cut in their minimum sentence.
The Tories have attacked the plans as a severe blow for relatives of victims.
MINIMUM MURDER SENTENCES
Confessing at earliest opportunity - 10 years
Pleading guilty at trial - 11 years and three months
Changing plea to guilty - 13 years and six months
Maintaining innocence - 15 years
The guidelines recognise the need to spare victims and witnesses the trauma of going to court where possible, by allowing lighter sentences for guilty pleas and co-operation.
Offenders who maintained their innocence until their trial but then pleaded guilty would be entitled to a one-quarter reduction in the minimum sentence they must serve.
Those who changed their plea to guilty after their trial had begun would be entitled to a one-tenth reduction.
Lord Woolf said it was extremely important for an offender to show "that he accepted he had acted contrary to the law and was prepared to take his punishment".
"It is very easy to say sorry - but to stand up and say, especially in the case of a serious crime, 'I have committed it, I know I have, I plead guilty, and I am going to take my punishment,' is an important factor.
"If they plead guilty at the last moment, they are still entitled to some credit - but it is less credit."
If the evidence against an offender was overwhelming, "there is not the same argument for granting a reduction as there would be in other cases", Lord Woolf added.
He said that in some cases the draft
guidelines would "almost certainly" allow a one-third reduction on the current
15-year standard tariff for murder.
"Someone who would get 15 years would now get 10 years," he said.
"The sentence remains life imprisonment. What it will mean is that you will come up for parole earlier than you would otherwise".
According to Lord Woolf, it will still remain the case that murderers will only be released if the Parole Board is satisfied that they are no longer a danger.
Shadow home secretary David Davis said: "What kind of message will this send?
"This would be a severe blow for friends and relatives of the murder victims and a discouragement to those who enforce law and order."
He said: "Parliament should set the sentencing guidelines. David Blunkett cannot claim to be tough on crime if he will allow murderers to walk free after just seven years.
"With over 800 murders a year, up by a sixth in only five years, this reinforces the need for punishments that deter killers."
Norman Brennan, director of the Victims of Crime Trust, was more vehement than the Tories in his criticism, accusing Lord Woolf of "losing the plot".
"Lord Woolf has an arrogant contempt for victims of crime and the law-abiding
public," Mr Brennan said.
"It's partly due to the lenient sentencing from judges that violent crime and
crime in general is spiralling out of control in the UK."
George Galli-Atkinson, whose 16-year-old daughter was killed after a driver mounted a pavement and struck her - and was not jailed - told BBC News: "We are at serious risk of undermining public confidence in the criminal justice system."
Harry Fletcher, of the National Association of Probation Officers, told BBC News cutting the average sentence murderers served would be "political suicide".
The guidelines also encourage judges to sentence some people to "weekend jails".
Such a sentence allows people to maintain jobs and family links while serving part of their week inside.
Lord Woolf said: "What we earnestly hope, as a result of these proposals, is that we will use
custody more effectively and more appropriately than we do now."