Prime Minister David Cameron has defended courts for handing out "tough" sentences for those involved in the riots across England.
Some MPs and campaigners say there were examples of terms being too harsh.
On Tuesday, two men were jailed for four years at Chester Crown Court for using Facebook to incite riots. One is to appeal against the sentence.
Lord Carlile, Lib Dem peer and Howard League for Penal Reform president, said some decisions were "questionable".
The barrister told the BBC "ringleaders should receive very long sentences" but warned "there was an issue of proportionality" over the way people already before the courts had been treated.
The PM said it was good that the courts were sending a "tough message".
Speaking in Warrington, he said: "It's up to the courts to make decisions about sentencing, but they've decided to send a tough message and it's very good that the courts feel able to do that."
In other developments:
- A fourth person has been charged with murdering three men who were hit by a car during riots in Birmingham. The 30-year-old man will appear in court on Thursday
- Prince of Wales and the Duchess of Cornwall visited
- Ex-Lib Dem leader Sir Menzies Campbell,
- Nottinghamshire Police say the disorder cost
- Metropolitan Police announces that more than 1,000 people
- teenager who represented her school as an Olympic Youth Ambassador
- banned from using social networking sites for 12 months
- jailed over the Facebook messages
So far, more than 2,770 people have been arrested in connection with last week's riots.
Some 1,297 people have now appeared before the courts, with the majority of charges relating to burglary, theft and handling, and violence and violent disorder offences.
In a statement, the Ministry of Justice stressed that the magistrates and judges were independent of government.
A spokesman added: "Their sentencing decisions are based on the individual circumstances of each case and offender.
"That is why different offenders may be given different sentences for what might appear to be similar crimes. To provide a consistent base for these decisions an independent body of experts, the Sentencing Council, set guidelines for them to use."
Meanwhile, the Courts and Tribunals Service says legal clerks in court have been advising magistrates to "consider whether their powers of punishment are sufficient in dealing with some cases arising from the recent disorder".
Magistrates are able to refer cases to crown courts which have tougher sentencing powers.
'Beyond the ordinary'
BBC legal correspondent Clive Coleman said the sentences being handed out across the country for offences of dishonesty such as theft, burglary and receiving stolen goods, suggested there were disparities between courts.
What the public was seeing may just be a "distorted version of the normal system", our correspondent said.
In another case, David Beswick, 31 from Salford was sentenced to 18 months in prison for handling stolen goods.
Our legal correspondent said under normal circumstances Beswick would have been given a mid-range community sentence.
Max Hill QC, vice-chairman of the Criminal Bar Association said it was not the job of judges "to deliver a political message on behalf of the government" when passing sentence but part of their role was to identify "serious aggravating features that elevate the crime beyond the ordinary".
He added: "In the case of the two in Chester, it seems that is exactly what the judge has done."
One serving judge, Charles Harris QC, told the BBC it was not possible for the courts to achieve absolute consistency in sentencing as "no two offences are the same".
"Judge and magistrates do look in the best way they can at the circumstances of the offence and the offender in front of them. In some cases, they might legitimately say, this goes beyond any existing guideline," he added.
Communities Secretary Eric Pickles told BBC Radio 4's Today programme: "We need to understand that people for a while thought that this was a crime without consequence - we cannot have people being frightened in their beds, frightened in their own homes for their public safety.
"That is why these kind of exemplary sentences are necessary. I think people would be rightly alarmed if that incitement to riot got off with just a slap on the wrist."