Fiona Onasanya is pictured arriving at the Old Bailey this morning

A Labour MP accused of plotting to avoid a speeding offence claimed in court yesterday that she was set up by her brother.

Fiona Onasanya, 35, accused her younger sibling Festus, 33, of forging her signature and going behind her back to make it look like she was not driving the car at the time.

In dramatic evidence to the Old Bailey, the trained solicitor said she was completely unaware about her brother's criminal behaviour and was shocked to learn of his plan.

However, prosecutors accused the Peterborough MP of 'working together' with her soul singer brother, suggesting she enlisted him 'to make the problem go away'.

Miss Onasanya, who as a Labour whip is in charge of party discipline, claimed she could not remember any details about what she was doing when her Nissan Micra was caught doing 41mph in a 30mph zone last year.

During cross-examination, she faced claims from the prosecution that she was in fact behind the wheel when the camera was triggered and was also using her phone at the time.

When she was sent a notice of intended prosecution (NIP) following the speeding offence in July last year, police received a response suggesting a man called Aleks Antipow was driving.

But a police investigation later found that Mr Antipow, a lodger at a property rented by the Onasanya siblings, was visiting his parents abroad at the time.

A still taken from a speeding camera shows the Nissan Micra, belonging to Labour MP Fiona Onasanya, as it is caught speeding on July 24 last year

The Labour MP acknowledged for the first time yesterday that her brother filled in the fake details on the police letter and signed it on her behalf.

Miss Onasanya told the court she had a close relationship with her brother, speaking to him several times a week and attending church together with him on most Sundays.

But she said the relationship has been 'strained' since both were charged with perverting the course of justice earlier this year.

'There is a lot that I didn't know about him,' she said. 'The person I believed he was is turning out to be someone different to the person I am seeing in evidence.

'I am his sister but things he has done I do not agree with and do not think it is acceptable.'

Onasanya (pictured left and right) confirmed that her mother Paulina Scott, brother Festus and friends and family could have had access to her car

The MP added: 'I think no-one is above making mistakes. He is my only brother. It is just him and my mum. I just don't understand why someone would do something like that. I would never have approved this.'

Mr Onasanya has pleaded guilty to three counts of perverting the course of justice, involving both the speeding offence concerning her car and two other offences.

His older sister, seen as a rising star in the Labour party, insisted that she had not known about her brother's previous ban for drink-driving or the nine penalty points on his driving licence.

She said the pair did not discuss the speeding offence in detail, claiming that her brother simply told her that it had been 'sorted out'.

But prosecutor David Jeremy QC said: 'There are not really hard feelings between you, you are just upset that you have been caught.'

Describing her defence as a 'charade', he added: 'Your defence has not been an exercise in disclosing the truth, it has been an exercise in evasion and concealing the truth.'

Fiona Onasanya (left) and her brother Festus Onasanya (right) are pictured arriving at the Old Bailey last week

Miss Onasanya denied claims by the prosecutor that 'the truth has given way to your professional ambition', claiming that a speeding penalty would have had no bearing on her career as an MP.

She admitted her brother had 'effectively set her up' by refusing to tell her that he had submitted false details for the speeding offence before they were quizzed by police January.

During cross-examination, Miss Onasanya said that she could not remember her movements on the day of the offence, claiming she was so busy that her assistants had to remind her to eat.

Asked whether she was curious about who was driving the car when it was caught speeding in Thorney, Cambridgeshire, and she received an NIP nine days after the offence, she said: 'No.'

The MP said she had assumed she was working in Westminster at the time of the offence on July 24 last year, despite the House of Commons having risen for summer recess at the time.

The trial continues.