A total of 38 cautions for rape have been issued in London over the past six years, the BBC can reveal.
Cautions for sex assaults on girls under 13 has increased
Figures released under the Freedom of Information Act showed that 1,291 cautions had been issued for sexual offences between 2001 and 2006.
The Crown Prosecution Service (CPS), insisted a caution for rape was only used in "exceptional circumstances".
But support group Women Against Rape (WAR) said it was a "slap in the face" for a woman if a rapist was cautioned.
The information supplied by the Metropolitan Police (Met) revealed 29 of the total cautions for rape involved children under the age of 16.
A further 50 cautions were issued between 2001 and 2006 for sexual assaults on children aged under 13.
And of these offences, those involving girls increased from 5 in 2004 to 12 in 2005 and 14 in 2006.
A spokeswoman for the CPS said that two points must be considered when looking at the figures for rape cautions.
"If an allegation of rape is made but they are cautioned for a lesser offence it is registered as a caution for rape," she said.
An admission of guilt is needed for a caution.
Admitting guilt means being put on the sex offenders register.
The caution will show up on a search of criminal records.
The CPS decides how to handle rape cases.
The CPS says cautions are only used in exceptional cases.
Rape carries a maximum life sentence.
"Also cautions are used in situations where there are exceptional circumstances such as if there are two very young people involved with learning difficulties."
A Met Police spokesman said: "The issue of a caution is a Home Office approved method of dealing with an individual after a thorough investigation has been completed.
"A caution is only given after serious consideration has been given to a number of factors and account has been taken of the public interest principles set out in the code for crown prosecutors issued by the CPS.
"A caution may only be given when the individual admits the offence. Every case must be judged on its merits.
"A caution may also be cited in court in any subsequent court proceedings and can be quoted on a Standard or Enhanced Disclosure issued by the Criminal Records Bureau and thus can be made known to a prospective employer."
But rape support group WAR said getting justice was essential to recovery after being raped.
"It's a slap in the face when the man is let off with merely a caution, a huge setback when you are trying to rebuild your life.
"Cautions confirm that the authorities hardly count what happened to you as serious."
The group said that cautions for rape were "the tip of the iceberg" as conviction rates had fallen to 5%.