The sentences handed to Arthur Labinjo-Hughes’s father and stepmother have been referred to the Court of Appeal for being too lenient.
The pair were convicted for killing the six-year-old, who was left with an unsurvivable brain injury while in the care of his father’s “evil” partner, Emma Tustin.
Arthur‘s body was also covered in 130 bruises.
Earlier this month, Tustin, 32, was found guilty of murder and handed a life sentence with a minimum term of 29 years.
Arthur’s father Thomas Hughes, 29, was found guilty of manslaughter and jailed for 21 years.
Both were also convicted of child cruelty.
The boy, from Solihull, West Midlands, was poisoned, starved and beaten by Tustin and Hughes in a prolonged campaign of abuse.
Speaking about the case, Attorney General Suella Braverman said: “My thoughts are with all those who loved Arthur Labinjo-Hughes.
“This is an extremely upsetting and disturbing case, involving a clearly vulnerable young child.
“Emma Tustin and Thomas Hughes grossly abused their position of trust and subjected an innocent child, who they should have been protecting, to continued emotional and physical abuse.
“I understand how distressing the public have found this case, but it is my job to decide if a sentence appears to be unduly lenient based on the facts of the case.
“I have carefully considered the details of this case, and I have decided to refer the sentences to the Court of Appeal as I believe them to be too low.”
A date for the hearing at the Court of Appeal is yet to be set.
The Unduly Lenient Sentencing scheme (ULS) allows victims of crime, their families, prosecutors and the public to ask for sentences for certain crimes to be reviewed.
The attorney general acts independently of government – as a “guardian of the public interest” – when deciding on ULS cases.
Earlier this month, it was announced there will be a national investigation into Arthur’s murder.
An independent national review will identify the lessons to be learned from Arthur’s death, in June last year, for the benefit of other children elsewhere in England.
The government also commissioned an urgent inspection of social care, health, police and probation services in Solihull to whom Arthur was known, in an effective upgrading of an existing local review.
In recent weeks, footballers and football fans across the country paid tribute to Arthur, who grew up supporting Birmingham City and also spoke of his dreams to play for Liverpool and Tottenham.
Supporters clapped for him in the sixth minute of matches.