Jo Cox, the MP for Batley and Spen, died from her injuries sustained in the horrific attack on Thursday.
The Batley and Spen MP was shot and stabbed by a man in Market Street at 12.53pm.
She was taken to Leeds General Infirmary but tragically passed away from her injuries.
West Yorkshire Police has launched a murder investigation into the senseless attack.
A 52 year old man named locally as Thomas Mair was arrested.
At a press conference, temporary Chief Constable Dee Collins said: "I am very sad to report she has died. I would like to express our deepest sympathies to her family and friends at this time.
"This is a very significant investigation. A full investigation is underway to establish the motive of this attack."
Reports that someone had been shot in Birstall shortly surfaced on social media around 1pm.
Social media rumours around 10 minutes later first suggested the victim was Batley and Spen MP Jo Cox. It is understood she was left lying severely injured on the pavement near Birstall library.
An eyewitness told the Examiner the man was shouting what sounded like "Britain First, Britain First."
A man in his late 40s to early 50s was slightly injured in the same incident.
This picture of the man said to be the attacker being arrested was circulating on social media but reports are unconfirmed.
Armed police were outside Leeds General Infirmary so it was understood Ms Cox was taken there for specialist high dependency treatment.
Labour shut its constituency offices in an emergency measure.
Shortly before 3pm the Vote Leave campaign suspended its Battle Bus.
Ms Cox was a supporter of the Remain campaign and reports are circulating that the attack was carried out by a man who shouted “Britain first.”