The lord chief justice has re-ignited the debate on the effectiveness of prison as a deterrent to crime.

Lord Woolf has warned the government that prison terms of less than a year do not help to rehabilitate offenders.

With the prison population standing at record levels, England's most senior judge said many of those sentenced to a few months should instead be ordered to undertake community service.

If politicians want to use sentences to give offenders a taste of jail, custody should be limited to no more than a month, he suggested.

Lord Woolf was speaking at a conference in Australia and anticipated a hostile reaction to his comments at home.

Earlier in the year he sparked a row within government when he argued that courts should not automatically hand down prison terms as a punishment for burglary.

The lord chancellor attracted a barrage of press criticism when he sided with Lord Woolf, while home secretary David Blunkett and the prime minister moved quickly to distance themselves from the idea.

But Lord Woolf remains insistent that measures must be taken to reduce prisoner numbers.

Overcrowding in Britain's jails was "a cancer eating at the ability of the Prison Service to deliver," the judge said.

"It is exacerbated by a large number of prisoners who should not be there, the most significant group being those sentenced to less than 12 months' imprisonment," he went on.

"It is now accepted on all sides that prisons can do nothing for prisoners who are sentenced to less than 12 months."

And two thirds of the 73,000 inmates would be reconvicted within two years of their release, he said.

"In many of those cases, the prisoners could have been punished in the community," he said.

"If prison was what was called for, the most appropriate sentence would be one of no longer than one month, to give the offender the experience of the 'clang of the prison door'."

Predicting a similar backlash to his comments on burglary, Lord Woolf pre-empted critics who will seek to brand him as "soft on crime".

"I recognise what I am about to say is capable of being labelled soft or liberal," he said.

"In fact, it is not soft, but realistic common sense. The effectiveness of a criminal justice system has to be judged by the extent to which it can deter crime and reduce the pattern of further re-offending."