Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. 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. Disgraced MP Fiona Onasanya will not have her three-month jail sentenced extended after the Solicitor General decided not to refer her case to the Court of Appeal. 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 in January but is continuing in her role despite calls for her to stand down.In the days after her conviction, the Attorney General’s office received a complaint insisting the three-month sentence was “unduly lenient”. The office had 28 days to consider the case, but on Monday, a spokeswoman for the Attorney General’s Office said: “After careful consideration the Solicitor General has concluded that he could not refer this case to the Court of Appeal.”A referral under the Unduly Lenient Sentence scheme to the Court of Appeal can only be made if a sentence is not just lenient but unduly so, such that the sentencing judge made a gross error or imposed a sentence outside the range of sentences reasonably available in the circumstances of the offence.”The threshold is a high one, and the test was not met in this case.”If the sentence had been found to be unduly lenient, the case would have been referred to the Court of Appeal which would decide whether or not to increase it. Onasanya was jailed for three months after she was found to have lied to police officers to avoid a speeding fine, becoming the first sitting MP in 28 years to be sent to prison. However, she has refused to resign as an MP, with her lawyer telling the Old Bailey that she had clung onto her seat because her £77,000 salary was her “only source of income”.Under existing laws MPs can only be ousted from Parliament if they are jailed for 12 months or more, meaning the authorities are powerless to prevent Onasanya from returning once she is released.Her constituents must also wait for her appeal process to end before they can attempt to unseat her and force a by-election, by which time the 35-year-old may already have returned to the Commons.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.