In a TV interview to be broadcast this morning, Lord Hailsham says that Mr Howard's plans to impose automatic life sentences for offenders with more than one conviction for violent crime or sex offences should be treated with "very grave suspicion".
The proposed extension of mandatory life sentences has brought widespread criticism from the judiciary, as it will mean that the Home Office rather than judges will rule when, if ever, lifers are released.
Lord Justice Rose warned last week that rapists might decide it was not worth their while leaving their victims alive if the penalties for rape and murder were identical. Earlier Lord Donaldson, former Master of the Rolls, said Mr Howard's proposed transfer of power could "leave it open to the executive to behave in a despotic manner".
In an interview to be broadcast on GMTV, Lord Hailsham says: "There is a mandatory life sentence, of course, for murder, and there is a mandatory death sentence, so far as I know, for high treason. But I am not sure that I am very keen on either. I think that to impose more of them is to encroach upon the independence of the judiciary."
But in a vigorous debate with judges in Northampton yesterday, Mr Howard said his proposed changes were necessary.
"As things stand, those who have committed two rapes or two violent offences have to be released without any assessment of risk unless a life sentence is passed," he said.
"They have to be released even if it is known that they continue to pose a risk. I just do not regard that as defensible."
A forthcoming white paper on sentencing will also call for minimum sentences for burglars and drug dealers - which would also limit judges' freedom to decide each case on its merits.
Mr Howard quoted Home Office research which he said showed that the average crown court sentence was 16 months for a first offence, but only 19 months for the seventh or more.
In magistrates' courts, where only 15% of burglars received immediate custody for a first offence, the average length of imprisonment for the first domestic burglary was just over three months. For the seventh, it was four months.
"There is surprisingly little progression in those figures," he said, "and I shall be taking them into account in considering the minimum length of sentence to propose."