Lord Irvine's pointed criticism came during a Lords' debate on the dangers of "judicial invasion of the legislative turf", which he himself had initiated. Senior judges have repeatedly criticised the Howard plans.
However, Labour backbenchers on the Home Affairs Select Committee yesterday backed an attempt to remove the Home Secretary's right to set tariffs for murderers serving mandatory life sentences and to decide whether or not they should be released.
Jack Straw, the shadow Home Secretary, pointedly declined to move from his previously held position that the Home Secretary's role should continue, although his office said last night that he would study the committee's report carefully.
In the debate, Lord Irvine said judges should not stray beyond their constitutional role as interpreters of enacted law.
Referring to suggestions by some senior judges - including Lord Woolf, the new Master of the Rolls - that the courts might in exceptional cases hold invalid statutes duly passed by Parliament, Lord Irvine declared that such an action would suggest "a judicial invasion of the legislature's turf.
"This causes ordinary people not only to think that the judges might have got over and above themselves, but that perhaps they are exercising a political function in judicial review cases instead of simply upholding the rule of law," he said.
Setting out Labour's attitude to the judiciary for the first time in the Westminster forum, Lord Irvine also criticised the recent suggestion by the new Lord Chief Justice, Lord Bingham, that the courts might feel compelled to act to protect the individual's right to privacy if legislation was not forthcoming.
"It sounds to ordinary people uncomfortably like a judicial threat to legislate."
Judges could only do that if there was a "clear community consensus that way. If there is no such consensus, and I am sure there is none, then I say they would seem to be taking sides. The result would be to imperil their major asset, their reputation for impartiality."
As to Mr Howard's sentencing proposals, they were, as senior judges had declared, "ill-judged", he said. "The present Home Secretary gives every impression of playing politics with the administration of justice.
"But if Parliament were to legislate for these proposals then that would be neither unconstitutional nor prejudicial to the independence of the judiciary," he continued.
"It is only if self-restraint is displayed on both sides that the public will have confidence that the separation of power is alive and well and working."Reuse content