Shadow Attorney General Emily Thornberry has written to Dominic Grieve about Stuart Hall's jail term to claim it was "unduly lenient".
Ms Thornberry has also urged the Attorney General to refer the issue to the Court of Appeal, saying, "This sentence surely cannot be strong enough for the seriousness and circumstances of the crime".
"Sexual assault is in itself a very serious offence and there were many aggravating factors present in this case ... Given all this, 15 months is not just a lenient sentence, it is unduly lenient.
She also called for Director of Public Prosecutions Keir Starmer to formally to refer the case to the Attorney General.