Home Secretary John Reid has criticised the sentence on a paedophile who abducted and sexually assaulted a girl of three as "unduly lenient".
Relatives of the victim of Craig Sweeney, 24, attacked his life jail term because guidelines on guilty pleas mean he could be out in five years.
The attorney general is examining Craig Sweeney's case after a request by Mr Reid and the Crown Prosecution Service.
Sweeney took the girl from her Cardiff home in January before attacking her.
Mr Reid asked for the sentence to be referred to the attorney general to the Court of Appeal, because the tariff "does not reflect the seriousness of this crime".
He acted after the family of the girl attacked Sweeney's sentence as "an insult".
A spokesman for the attorney general said: "The attorney has called for the file in Craig Sweeney's case in order to consider whether to refer the sentence to the Court of Appeal as unduly lenient.
"The attorney will make a decision purely on the merits of the case and not in response to political or public pressure. Calling for the file in no way implies that there will be a reference by the attorney. Still less does it imply any criticism of the sentencing judge."
BBC Political Editor Nick Robinson says he understands Lord Goldsmith feels the home secretary's intervention is "not terribly helpful" because it is the attorney general's responsibility to make his case on legal grounds.
But relatives of the girl have welcomed Mr Reid's intervention and called on the government and judiciary to ensure such crimes were "properly punished".
"We have seen examples in the past where the Home Office has intervened where it is felt that sentences are too lenient, only for the courts to increase those sentences by a minimal amount," said Anne Tyson, a solicitor representing the victim's family.
"We now hope that this intervention by the Home Office will mean that justice is served in this case with a significant increase in the sentence and that it serves as a benchmark for punishing the perpetrators of these horrific crimes in the future."
Earlier this month, five judges at the Court of Appeal increased the minimum jail sentence on Alan Webster, convicted of raping a 12-week-old baby, after the case was referred to them by the attorney general.
However, the victim's family said the increase - from six years to eight - was "simply not enough".
A Home Office spokesman said: "Life sentences are the ultimate sanction a court can make.
"However, the home secretary is concerned that the tariff Craig Sweeney has been given does not reflect the seriousness of this crime."
Chris Woolley, the chief crown prosecutor for south Wales, said Judge John Griffith Williams QC was acting in accordance with guidelines in sentencing Sweeney at Cardiff Crown Court.
Sweeney admitted carrying out sex assaults at this Newport flat
"The judge has to determine first of all the notional sentence, which in this case was 18 years," he said.
"Then that is cut by half to reach the actual sentence. Then the judge is obliged to cut a third off in view of the guilty plea."
Sweeney - who was known to the family - had snatched the girl from her home after she had returned home from a shopping trip and while her mother made a telephone call.
He drove her to his Newport flat where he was living after being released early from a three-year sentence for indecently assaulting a girl aged six. There she was sexually assaulted.
She was only found by police hours later in Wiltshire, after a car chase prompted by Sweeney having no lights on his car and jumping red lights.
He drove erratically at speeds of up to 100mph with the girl in the car.
Roger Hill, of the National Probation Service, said the case had exposed weaknesses in the criminal justice system.
He called on the police, the probation service, the Prison Service and the Parole Board to work more closely together to manage offenders in the community.
New sentencing powers put in place by the government will mean the probation service can influence if and when Sweeney is released from the new prison sentence, he said.
John Charles Rees QC, who represented Sweeney in court, said he did not attempt to minimise his client's actions.
Describing his client as "depraved", he said Sweeney had pleaded guilty "without reservation" and argued that he recognised the seriousness of his offences.
He also said there was no medical evidence the toddler had suffered any "serious, permanent medical damage" from her ordeal.
He said there was no more than a "possibility" of psychological damage in the long term.
The family of the girl also attacked South Wales Police's initial handling of the incident and their complaint is being investigated by the Independent Police Complaints Commission (IPCC).
South Wales Police said it would be inappropriate to comment while the investigation by the IPCC was still ongoing.