Fiona Onasanya arrives at the Old Bailey for the sentencing that made her the first sitting MP to be jailed in almost 30 years - gavin rodgers/pixel8000

The first sitting MP to be jailed in three decades will continue to receive her taxpayer-funded salary behind bars, and Parliament is powerless to oust her.

Fiona Onasanya, a former Labour whip, was sentenced at the Old Bailey on Tuesday to three months in prison after being convicted for lying to police officers to avoid a speeding fine.

The Peterborough MP, who was caught speeding less than two months after being elected in 2017, has been urged to resign by the Labour Party but has indicated that she will continue serving from prison.

A source close to the 35-year-old, who was expelled by Labour last year, told The Telegraph that she had allegedly made no contingency plans for being jailed, adding they believed she was intent on staying on.

Her lawyer, Christine Agnew QC, told the court that Ms Onasanya had chosen not to resign because her £78,000 salary was “her only source of income”.

It means that Ms Onasanya will continue earning a weekly salary of £1,480 and receive pension contributions amounting to £9,000 annually whilst incarcerated.

She will also be entitled to claim thousands of pounds in expenses, including her £625 monthly rent, staff wages and the running of her constituency office.

Festus Onasanya, the MP's brother, arrives at the Old Bailey Credit: gavin rodgers/pixel8000

Her brother Festus, 34, was also convicted for conspiring with her to pervert the course of justice and sentenced to 10 months in prison.

Under existing laws, MPs can only be automatically ousted if they are jailed for 12 months or more, meaning the authorities cannot intervene.

Her constituents, meanwhile, will have to wait weeks before learning whether or not they will be able to remove her from office and trigger a by-election, as she has decided to appeal her conviction.

The Commons Speaker, John Bercow, will only be able to trigger a recall petition - a ballot of her constituents - once her appeal process has ended and if her conviction is upheld.

The image of Fiona Onasanya's Nissan Micra picked up by a speed camera Credit: PA

The Telegraph understands that Labour has already begun the process of approaching candidates to replace her in a by-election, which will only be called if 10 per cent of her constituents vote for one.

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However, she could still choose to contest the seat again and will be able to wage the campaign as an independent candidate.

Amid a public backlash, senior Labour and Conservative MPs demanded an urgent overhaul of parliamentary rules to ensure that future convictions lead to automatic expulsion.

They included the former London Mayoral candidate Zac Goldsmith, who told The Telegraph that Ms Onasanya’s case highlighted the current parliamentary safeguards were open to abuse.

Mr Goldsmith, whose previous calls for reform were ignored by MPs in 2014, said: “I warned that a time would come when voters realised they had been conned and that is now what has happened.

“The fact that voters are lumbered with an MP who has been convicted and jailed shows unambiguously that the ‘Recall’ system we have is nothing more than a pretence.”

He was joined by Labour’s Lucy Powell, who said it was “totally wrong that an MP can continue to be paid whilst in prison”, adding that her behaviour “shames us all”.

“This case highlights what more we still need to do to ensure we are seen to be treated the same as everyone else,” she added.

Jess Phillips, the Labour MP for Birmingham Yardley, added: “We must change our rules accordingly.”

A Labour spokesman said Ms Onasanya had “let the voters of Peterborough down”, adding that her conviction offered her “one last opportunity to act honourably and resign from Parliament.”

“If Fiona does not resign, Labour will support local residents in their efforts to trigger a by-election,” they continued. “Labour will fight any by-election vigorously.”

However, her press secretary said there was “still an office to be run”, adding that “myself and the rest of the team here will be doing the best they can for constituents”.

Sentencing Ms Onasanya on Tuesday, Mr Justice Stuart-Smith said she had “not simply let herself down” but also those “who look to you for inspiration, your party, your profession and Parliament”.

"You had a clean licence and were well able to pay any fine that would have been imposed and a speeding offence would have been no real or lasting embarrassment to you as a Member of Parliament,” he added.

“The fact remains that, both as a solicitor and a Member of Parliament, you are fully aware of the importance of upholding the proper administration of justice.”

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