The Peterborough MP was convicted at the Old Bailey of perverting the course of justice after lying to police to avoid a speeding charge.
She was jailed this week but is continuing in her role despite calls for her to stand down.
The 35-year-old solicitor's sentence will now be reviewed.
A spokesman for the Attorney General's Office said: "We have received a request for the case of Fiona Onasanya to be considered under the unduly lenient sentence scheme.
"The Law Officers have 28 days from sentencing to consider the case."
If the sentence is found to be unduly lenient, the case will be referred to the Court of Appeal which will decide whether or not to increase it.
Parliamentary rules require the removal of an MP who is jailed for 12 months or more.
A lesser sentence can result in a recall petition, which can force a by-election if it is signed by more than 10 per cent of the electorate in the constituency.
Onasanya, an Independent after being expelled by the Labour Party, is appealing against her conviction.
Jurors at the Old Bailey heard that Onasanya colluded with her brother Festus after her car was clocked doing 41mph in a 30mph zone in the village of Thorney, near Peterborough, in July 2017.
The court was told that she was sent a Notice of Intended Prosecution (NIP) to fill out, but it was sent back naming the guilty driver as Aleks Antipow, an acquaintance of her brother, who was away visiting his parents in Russia.
Her brother received 10 months in prison after he pleaded guilty to three counts of perverting the course of justice over speeding, including over the July 24 incident.
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