The offence of murder should be reclassified in England and Wales to reflect levels of seriousness, the government's legal advisers have urged.
The Law Commission has suggested a US-style system
The Law Commission wants a new system of first and second degree murder and a more limited manslaughter prosecution.
It could mean mandatory life terms for murder being reserved for cases where an intention to kill was clear.
Some cases currently treated as manslaughter would be prosecuted as second degree murder.
The report is part of the first major rethink of murder laws in England and Wales for over 50 years.
Currently all those convicted of murder must receive a life sentence but judges recommend a minimum term or "tariff".
The foundation of the proposed framework was that the mandatory life sentence "should be confined to cases where the offender intended to kill", Tuesday's report said.
"Taking a risk, even a high risk, of killing someone is recklessness and is very serious but it is not the same as the deliberate taking of life," it added.
Under the plans, killers who intended to cause their victims "serious harm" but not to kill would be prosecuted for second degree murder and would therefore not face a mandatory life sentence.
The second tier would also include killings through "reckless indifference" and cases where the killers were provoked, suffered diminished responsibility or were under duress.
Law Commission chairman Sir Roger Toulson said the second tier of murder was being suggested "to bring up into murder, cases which at the moment aren't there and we think should be".
The current murder laws, dating back to the 17th Century were "archaic and misleading", he said.
But the proposals were "in no sense set in stone", he added.
"We want to know what people think and why."
Manslaughter would be brought against someone who killed by "gross negligence" or "intentionally or recklessly causing harm".
'Licence to murder'
But Dominic Grieve, the Conservative spokesman on legal affairs, said he had reservations about "tinkering with the principle that murder leads to a life sentence".
"Murdering somebody is a very serious matter and the rule is that a person shouldn't necessarily spend the rest of their life in prison, but should be capable of recall to prison if their behaviour after release gives rise to concern," he told BBC Radio 4's Today programme.
And the Victims of Crime Trust, which represents families of murder victims, said the plans would "do nothing to reassure the British public".
LAW COMMISSION PROPOSALS
First degree murder: Intention to kill unless defendant has partial defence
Mandatory life sentence
Second degree murder:
i) intention to cause serious harm (currently murder)
ii) killing through reckless indifference to causing death (currently manslaughter)
(iii) intentional killing where a partial defence applies (currently manslaughter)
Discretionary life sentence or fixed jail term
Manslaughter: Gross negligence or deaths caused by intentionally or recklessly causing harm
"These proposals will result in shorter sentences and it will be seen by a number of criminals as a licence to murder, as a long term of imprisonment seems less likely," director Norman Brennan said.
Metropolitan Police chief Sir Ian Blair, meanwhile, said he welcomed "degrees of murder".
"There is something here about making sure that the deeply premeditated, hideously cruel murder of children, or murder and terrorism, or whatever, is at one end of the sentencing scale which, again, is open and transparent, and a mercy killing is at another," he said on LBC Radio's Nick Ferrari at Breakfast show.
"I'd much rather have that than have many, many more manslaughter verdicts," he added.
Liberal Democrat legal affairs spokesman Simon Hughes broadly welcomed the plans but said that the debate over them "must take into account and respect" the views of people who had lost loved ones through violence.
The options suggested by the commission will be put out to consultation before it presents a final set of recommendations to the Home Office next Autumn.
Last year, the commission condemned the law on murder as "a mess" and said a major rethink was needed because of the "breadth and depth of discontent" with the current situation.
The review, announced last October, is the first wholesale examination of murder laws since the Royal Commission on Capital Punishment which ran from 1949 to 1953.
This led to the Homicide Act, which was passed in 1957.