Arthur was left with an unsurvivable brain injury while in the sole care of his 32-year-old stepmother Emma Tustin. Tustin was jailed for life with a minimum term of 29 years at Coventry Crown Court on Friday, after being convicted of murder by assaulting Arthur in the hallway of her Cranmore Road home in Solihull, on June 16, 2020.
Little Arthur, whose body was also covered in 130 bruises, died in hospital the next day.
His father, Thomas Hughes, 29, was sentenced to 21 years for manslaughter.
The Attorney General’s Office (AGO) has confirmed the sentences issued to Tustin and Hughes will be reviewed.
Peter Halcrow, 61, the maternal grandfather of Arthur, said the couple “must never see the light of day again”.
Speaking on Friday, the Prime Minister said ministers will leave “absolutely no stone unturned” to establish what went wrong in the case of Arthur.
He said: “I just want to say, on the tragic and appalling case of Arthur Labinjo-Hughes, like many people I find it hard to read it, let alone to understand how people could behave like that to a defenceless little child.
“I’m glad that justice had been done, in the sense that they have both received tough sentences, but that is absolutely no consolation, and what we’ve got to make sure now is we learn the lessons about that case, we look at exactly what happened, what else could have been done to protect that child.
“It is early days, but I can tell you this, we will leave absolutely no stone unturned to find out exactly what went wrong in that appalling case.”
The AGO has 28 days from the date of sentence to review a case, assess whether it falls under the Unduly Lenient Sentence scheme, and make a decision as to whether to refer a sentence to the Court of Appeal.
The Court of Appeal then makes a ruling on cases which have been referred.
A spokesperson for the AGO said: “The Attorney General’s thoughts are with those who loved Arthur.
“I can confirm that the sentences given to Emma Tustin and Thomas Hughes have been referred to the Attorney General for review to determine whether they were too low.”