The judges' actions were described as "highly unusual"
The body which represents 652 judges in England and Wales has attacked government proposals to introduce compulsory guidelines on sentences.
The Council of Circuit Judges said the government's plans were "unnecessary, costly and unwelcome".
The Council said the imposition of mandatory guidelines "may result in injustice to both offenders and victims in individual cases".
But Justice Secretary Jack Straw said judges' discretion would remain.
The plans are contained in the Coroners and Justice Bill, which had its third reading in the Commons on Tuesday and will now go to the Lords.
BBC Home Affairs correspondent Danny Shaw said it was "highly unusual" for the judiciary to make such a statement.
'Result in injustice'
The government is looking to introduce a sentencing council which would impose rigid guidelines for judges.
This would allow them to more accurately predict what would happen to the prison population.
But the council said this move would remove judges' ability to use discretion.
The statement said: "We do not believe that the introduction of mandatory guidelines will facilitate the just and proper sentencing of offenders.
"We consider it may result in injustice to both offenders and victims in individual cases. For example the position of some female offenders, young offenders and those in minority or disabled groups may be prejudiced."
But Mr Straw insisted he had made clear in Parliament on Tuesday judges' discretion would be preserved.
He said he had introduced a series of amendments to the bill to "underpin judicial discretion, and to ensure greater necessary flexibility for the sentencing court".
Mr Straw added: "In any event, the Bill spells out that the sentencing court can depart from the already flexible guidelines 'where it is in the interests of justice to do so'."
He added that he had followed the recommendations of Lord Justice Gage's independent working group throughout and offered to discuss council members' concerns with them.
A Ministry of Justice spokesman said greater consistency in sentencing would be in the interests of both justice and the public.
"We are not proposing a sentencing matrix or any mandatory guidelines, nor does the government have any intention of removing judicial discretion from sentencing in individual cases," the spokesman added.