A Labour MP deliberately misled the police and became “trapped in a number of lies” after blaming a former lodger for driving her speeding car, a court has heard.

Fiona Onasanya, the MP for Peterborough, was accused at the Old Bailey of colluding with her brother to pervert the course of justice after her Nissan Micra was recorded driving over the speed limit in July 2017.

Her brother Festus Onasanya, 33, admitted three counts of perverting the course of justice, a week before he was due to face trial.

Onasanya, a former solicitor, named Aleks Antipow as being behind the wheel on official forms, but the prosecution claims he was at home with his parents in Russia.

David Jeremy QC, opening the case for the prosecution, said Fiona Onasanya had deliberately planned with her brother to deceive the police. They adopted a method that had been used by Festus Onasanya to try to avoid speeding offences on two other occasions, he said.

“It must, as some of us will know, be very irritating to receive that bit of paper telling us that we have triggered a speed camera and asking us to own up or name the driver.

“But while irritation is understandable, telling lies to frustrate an investigation into an offence is not. What Miss Onasanya did when her vehicle was trapped on 24 July 2017, was not to own up and tell the truth but was to adopt her brother’s system of evading prosecution.

“The two of them were acting jointly in telling lies in order to prevent the prosecution of the true driver,” he told the jury at the Old Bailey in central London.

Onasanya’s car was caught by a speed camera on the B1167 in Thorney, Cambridgeshire, the court heard. The driver was travelling at 41mph in a 30pmh zone.

She was sent a formal letter entitled a Notice of Intended Prosecution (NIP) by Cambridgeshire police a week later. It was returned with her signature and claimed that the vehicle was being driven by Antipow when the offence took place, the prosecution alleged.

Antipow was not the driver who committed the July 2017 offence but was instead a former tenant who had lived for a month in a property which was jointly rented by Onasanya and her brother, the prosecution said.

The telephone number attributed to Antipow on the NIP form belonged to a firm for which Onasanya’s brother had worked as a delivery driver, Jeremy said.

Police examined Onasanya’s mobile phone records and found that both of her mobile phones were in Thorney at the time the offence took place, the prosecution claimed.

“Where was she? Was someone else using both of her phones? Was someone else driving her car? What sort of a coincidence would it have had to have been for her phones and car to be in the area?” said Jeremy.

After Cambridgeshire police received no response from Antipow at the address supplied on Onasanya’s form, they wrote to the MP in September 2017 asking her for Antipow’s correct details.

She replied: “I have provided a completed nomination previously,” the court heard.

After again receiving no reply from approaches to Antipow’s supplied address, police approached the MP by email and letter for further help but she did not respond, the court heard.

An investigator for the police’s ticket unit eventually contacted Onasanya at her parliamentary office in November, the court heard. In a telephone conversation, she claimed that Antipow filled in his own details, it was alleged.

Onasanya was informed by the investigator that the telephone number attributed to Antipow on her NIP form was the same number attributed to a different driver of her brother’s car in a separate driving offence.

The address attributed to Antipow on the form was Onasanya’s brother’s former residence, the court heard.

The MP was interviewed under caution by police in January without a solicitor, the court heard. She gave no answer to questions asking if she was driving her car when it was caught speeding, or if she had signed or written the NIP form, the prosecution alleged.

Jeremy said the case had started about speeding but had become focused on whether the MP had lied. “As a result of the choices made by Miss Onasanya, [it has become] a case about lying … Lying in a way that has had to be coordinated with lies told by her brother. Lying to avoid prosecution for a breach of the laws that apply, or should apply, to every single one of us,” he said.

The MP’s brother, a singer who lives with his mother in Chesterton, Cambridge, pleaded guilty last week to perverting the course of justice in relation to the incident.

He also pleaded guilty to two further charges of perverting the course of justice, which involved blaming someone else for two separate speeding incidents on 17 June and 23 August last year.

Festus Onasanya was bailed by Judge Nicholas Hilliard QC and is due to be sentenced at the conclusion of his sister’s trial.

Fiona Onasanya, who was a solicitor before her election to parliament in 2017, is a Labour whip, responsible for party discipline.

She has denied perverting the course of justice. The case continues.