Home Secretary John Reid has denied telling judges to give criminals softer sentences to ease prison overcrowding.
He said he was merely re-stating existing guidelines and serious offenders should still be locked up.
It comes after two judges released sex offenders, saying they were following Mr Reid's advice.
Mr Reid also said he was "sad" over England and Wales Youth Justice Board head Rod Morgan's decision to quit over overcrowding in youth prisons.
The home secretary has been under fire on prison overcrowding after he wrote to judges and magistrates asking them to imprison only the most dangerous of offenders.
The Conservatives accused Mr Reid of failing to protect the public and presiding over "anarchy" in his department, after two sex offenders were released by judges who said they would normally have been locked up.
But Mr Reid insisted the guidelines had had not changed.
He told the BBC: "The guidelines under which they operate are exactly the same this week as they were last week and they were the week before. They have been the same for several years.
"Violent, persistent, serious offenders should be given custodial sentences - or sentences that protect the public - but if they aren't, if they're less serious, or not dangerous to the public, then they should be put to either paying fines or community service, to pay back to the public."
He said he had written to the judiciary because home secretaries had to remind them of sentencing guidelines "from time to time".
His words echo earlier comments by Prime Minister Tony Blair, who said the judges may have misunderstood the government's advice.
"Yes, there's pressure on prison places - but if somebody's a danger to the public, there's no question of where they should be," said Mr Blair.
Earlier, Judge Graham Cottle said he had released 46-year-old Keith Morris, facing a maximum of 14 years in jail for serious sex offences, on bail pending a pre-sentence report because of prison overcrowding.
"If this case had been here last week it would have been over by now and he would be in Exeter Prison," Judge Cottle told Exeter Crown Court.
This follows a case on Thursday where Judge John Rogers QC gave a man convicted of child porn offences a suspended sentence because he had to bear in mind "the current sentencing climate".
Another judge, Richard Bray, sitting at Northampton Crown Court, said politicians should wake up to the fact prisoners were reoffending "because judges can no longer pass deterrent sentences".
Meanwhile, in an interview for BBC Two's Newsnight, youth justice chief Rod Morgan said youth courts and children's prisons were being "swamped" with minor offenders who were "cluttering up" the system.
Echoing the row with adult prisoner places, the professor told Newsnight: "We're standing on the brink of a prisons crisis.
"We have tonight lots of people in police cells because there is no space for them in custody and that's true for children and young people also.
"I regard a 26% increase in the number of children and young people that are being drawn into the system in the past three years as swamping."
A Home Office spokeswoman said: "We refute the claim that young people are being demonised and criminalised."
But she added: "We remain unapologetic about the need to tackle anti-social behaviour by anyone, regardless of their age."
Figures released earlier show the prison population in England and Wales is at bursting point, having reached 79,731, an increase of 356 on last Friday.
In a separate development, Mr Reid admitted the government acted "unlawfully" in relation to the detention of young asylum seekers.
The admission that the detention policy "did not strike the right balance" came in High Court test cases in which detained children who said they were under 18 are seeking damages for loss of liberty.
Commenting on the Home Office's mounting troubles, shadow home secretary David Davis said: "The prime minister and home secretary's initiatives are looking less like an agenda for respect and more like an agenda for anarchy."
Tory leader David Cameron said ministers had to stop "rearranging the chairs" on the stricken Home Office ship and "get their sleeves rolled up and deal with this crisis".
Liberal Democrat leader Sir Menzies Campbell said the resignation of the head of the youth justice board for England and Wales underlines the "shambles" at the Home Office.