Rape is rape. This is not only absolutely correct in moral terms, it is also literally correct as a matter of law. The offence is under section 1 of the Sexual Offences Act:

Rape

(1)A person (A) commits an offence if --

(a)he intentionally penetrates the vagina, anus or mouth of another person (B) with his penis,
(b)B does not consent to the penetration, and
(c)A does not reasonably believe that B consents.

(2)Whether a belief is reasonable is to be determined having regard to all the circumstances, including any steps A has taken to ascertain whether B consents.

(3)Sections 75 and 76 apply to an offence under this section.

(4)A person guilty of an offence under this section is liable, on conviction on indictment, to imprisonment for life.

As a matter of criminal liability, the law does not distinguish between different types of rape. Section 1 always applies regardless of the circumstances of the rape.

The unfortunate and offensive comments today of Justice Secretary Ken Clarke did not mean, and were not intended to mean, that there is or should be any change to this simple important fact.

So what was Ken Clarke on about? The answer to this lies in how the criminal law deals with the rapist on conviction. For although the criminal offence is always the same whatever the rape, the sentencing will be different in different cases. Unlike murderers, whom always have a supposed "life" sentence, not all rapists get the same sentence. Some rapists receive heavier sentences than others; but this also means, by implication, that some rapists will get lighter sentences.

According to the Crown Prosecution Service sentencing guidelines, the custodial sentences which will usually follow conviction go from 4 to 8 years for a single offence of rape of an adult victim, to 19 years for the repeated rape of same victim over a course of time or rape involving multiple victims. Looking at the various permutations in the guidance makes one realise that it is not just Clarke who regards some rapes as worse than others: it is settled sentencing policy.

Should this be the case? Why can there not be a single sentence for rape, regardless of the circumstances? There is a good argument for this, though even with "life" for murders, different murderers get different tariffs.

However, looking at the permutations in the CPS guidance, there do appear to be situations where heavier sentences seem justified, either because of the age of the victim or because of certain express "aggravating" factors: the offender ejaculated or caused victim to ejaculate; there was a background of intimidation or coercion; there was use of drugs, alcohol or other substance to facilitate the offence; there were threats to prevent victim reporting the incident; there was abduction or detention; the offender aware that he is suffering from a sexually transmitted infection, or pregnancy or infection results.

Views may differ as to whether these should be aggravating factors or not. But unless the contention is that all sentences should be the same for rape regardless of any aggravating factors, then some rapes will be dealt with more severely (and hence some rapes dealt with more leniently) than others.

Should there be a discount on the sentence if the rapist pleads guilty? Here, there is the argument that the offender should be encouraged not to put his victim through the trauma of cross examination. If this argument is valid, the question becomes how should this be achieved -- if it is not by discounting the sentence, then it is actually difficult to see what is the alternative.

The background to Clarke's comments is that Ministry of Justice is currently consulting generally on sentencing. This is the review which Clarke was referring to in his interview. As regards Clarke's particular comments, a spokesperson at the Ministry of Justice said:

Anyone who commits a serious violent or sexual offence will continue to receive a long prison sentence. We have always had a reduced tariff for early guilty pleas in this country, it already stands at a third. The 50 per cent discount is the maximum reduction under consideration. It will only be available for those who plead guilty at the earliest opportunity. It will certainly not apply to every guilty plea, only if offenders plead at the earliest opportunity. Judges will of course retain discretion over sentences in individual cases. It is right that we continue to incentivise early guilty pleas. They can reduce the number of victims of crimes such as rape who are forced to relive the trauma that they suffered and be subject to cross-examination in court.

Clarke's comments were unfortunate and seemed to betray a complacency about rape. What he said implied that he did not take all rapes seriously. It is entirely right that he is criticised for what he said and the way he said it.

But the facts remain: the criminal justice system does distinguish between different types of rape, some sentences are harsher or more lenient than others, and there is merit in encouraging early guilty pleas.

It may well be that sentences for rape across the board are far too low; I certainly think so. Rape is a uniquely horrific crime which should be treated more severely than other offences. However, that rape is rape does not mean that all rape sentences are equal. But does it mean that they should be?

David Allen Green is legal correspondent of the New Statesman