A man is in custody over the stabbing and shooting death of British politician Jo Cox. Courtesy: Today/Nine Network

BRITISH Labour politician Jo Cox has died in hospital after being shot and stabbed by a man reportedly shouting ‘Britain First’ just a week out from the Brexit vote.

Ms Cox, 41, succumbed to her injuries about an hour after the attack, and was pronounced dead at 1:48pm local time (11pm AEST).

Police have a 52-year-old man in custody, who The Sun names as local Tommy Mair, as well as an old fashioned gun and a long knife.

Acting Chief Constable Dee Collins said the police believe it was a “lone gunman” acting on his own.

Jo Cox was one of the "brightest" and "most popular" MPs, says Home Secretary Theresa May https://t.co/47qcYDe8sl — BBC Newsbeat (@BBCNewsbeat) June 16, 2016

“The most important fact here at the moment is that we have one male under arrest,” she said. “There was a further attack on a 77-year-old man who sustained injuries that are non life threatening.”

She said a number of addresses were being searched in relation to the incident.

The Times has reported that Cox was due to recieve extra security from police after being harrassed in a string of messages over three months.

Tomorrow's front page: Murdered MP had faced string of security threats #Tomorrowspaperstoday pic.twitter.com/t5pSdBhXpT — The Times of London (@thetimes) June 16, 2016

Extra security was being considered for her constituency in Bristall where the attack occured as well as her houseboat in London.

No link has been made between the harrasment and the attack.

The Sun reports eyewitness Hithem Ben Abdallah said Ms Cox got involved in a scuffle between two men in the village of Birstall near Leeds.

Mr Abdallah said one of the men was fighting with Ms Cox and then a gun went off at least twice and “she fell between two cars and I came and saw her bleeding on the floor.”

After around 15 minutes, the shop owner said emergency services arrived and tended to her with a drip.

Another man, who runs a nearby cafe, told The Telegraph she was shot three times, including once in “the head area”, before being stabbed multiple times with a “foot-long knife”.

Police escort an ambulance to a #Leeds hospital after a shooting in #Birstall pic.twitter.com/Z5z6OZ8BLX — BBC Look North (Yks) (@BBCLookNorth) June 16, 2016

“Three times she was shot, the initial time which then she dropped to the floor and two more times,” the man said. “The third time he got proximity he shot her round the head area.”

“In the meantime he was stabbing her as well, he was stabbing her with his knife,” he said.

“He was stabbing her with a foot-long knife multiple times while shouting Britain First, Britain First, Britain First.”

Britain First is the name of a right-wing group that describes itself on its website as “a patriotic political party and street defence organisation”.

Jayda Fransen, deputy leader of Britain First, said the attack was “absolutely disgusting” and suggested Britain First was a common slogan being used in the EU referendum campaign by those who support Brexit.

JO COX SHOOTING: Britain First official statement - https://t.co/S7etYC2Mmh pic.twitter.com/s2UlWZgxiA — Britain First (@BritainFirst) June 16, 2016

“We were as shocked to hear these reports as everyone else,” Ms Fransen said. “At the moment we would point out this is hearsay, we are keen to verify the comments but we can only do that when the police provide more details.”

Ms Cox had recently pushed for England to remain in the European Union ahead of the June 23 Brexit vote.

The rival referendum campaign groups said they were suspending activities for the day and Prime Minister David Cameron said he would pull out of a planned rally in Gibraltar, the British territory on the southern coast of Spain.

“It’s right that all campaigning has been stopped after the terrible attack on Jo Cox,” he said on Twitter.

Ms Cox was attacked while at an advice surgery. Advice surgeries are periodical events where politicians can speak with their constituents needing assistance.

The gunman reportedly lived in a small semi detached house on the Field Head council estate in Birstall.

The neat semi in Lowood Lane was cordoned off and under police guard as neighbours spoke of the “very quiet but very helpful” suspect, reports The Telegraph.

They said that Mair had lived in the house for more than 30 years and was living with his grandmother until she died about 20 years ago. Since then he has lived on his own and has never had any full time employment.

Jo Cox RIP pic.twitter.com/KDTpEzyzBA — Christian Adams (@Adamstoon1) June 16, 2016

Neighbour Kathleen Cooke, 62, said: ”I am really shocked. He walked past my house this morning and said hello like he always does. He was wearing a grey T-shirt and his white baseball cap like he always does and he was carrying a small rucksack.

In 2010 a Thomas Mair, then aged 46, was quoted in his local paper talking about his mental health issues.

He volunteered at the Oakwell Hall country park in Birstall in 2010 after being a patient of the Mirfield-based Pathways Day Centre for adults with mental illness, according to a Huddersfield Examiner report at the time.

“I can honestly say it has done me more good than all the psychotherapy and medication in the world,” he told the paper. “Many people who suffer from mental illness are socially isolated and disconnected from society, feelings of worthlessness are also common, mainly caused by long-term unemployment.”

Pathways is described on the South West Yorkshire Partnership NHS Foundation Trust website as a “team that offers support to people experiencing mental health difficulties”.

Neighbours said they did not think he had a job or drove a car and described how he would do gardening chores for local people.

David Pickles said: “He’s lived there longer than me and I’ve lived here since 1975. I still can’t believe it. He’s the last guy I would have thought of.

“He’s just quiet. He kept himself to himself. He lived by himself. He’s been on his own for about 20 years.

Mr Pickles said he did not know of any connection between his neighbour and Ms Cox.

Another neighbour, who did not want to be named, said: “We’ve known him quite a lot of years. I’ve known him since I was young. He lived with his grandmother in that house, she died a few years ago. He was a bit of a loner. It’s a bit of a shock - he did everyone’s gardens.

“I can’t say a wrong word about him, he was so quiet. It’s come as a shock to everybody.”

Leah Ainley, who lives in Risedale Avenue where Mair was arrested, said armed police surrounded him and pinned him to the ground.

“I just saw them take him down and catch him,” she added.

“The police were armed. There were more than 10 of them at the end. I just looked out the window and saw them. The man was white and bald. He banged his head on the floor. He just lay on the floor while they were holding him down.

“He had a bag with him but that’s all I saw, I didn’t see if he was armed.”

The death of Jo Cox is a tragedy. She was a committed and caring MP. My thoughts are with her husband Brendan and her two young children. — David Cameron (@David_Cameron) June 16, 2016

My heart is broken. She was amazing a brave giant who stood against bullies. — Jess Phillips MP (@jessphillips) June 16, 2016

Ms Cox’s husband, Brendan Cox, posted an image of her on Twitter after she was attacked.

The couple have two children together.

After news of her death he called on people around the world to unite against hate.

“Today is the beginning of a new chapter in our lives. More difficult, more painful, less joyful, less full of love. I and Jo’s friends and family are going to work every moment of our lives to love and nurture our kids and to fight against the hate that killed Jo,” the statement said.

“Jo believed in a better world and she fought for it every day of her life with an energy, and a zest for life that would exhaust most people.

A quote from Jo Cox's maiden speech to the House: pic.twitter.com/WVqzDFCXoj — TheLitCritGuy (@TheLitCritGuy) June 16, 2016

“She would have wanted two things above all else to happen now, one that our precious children are bathed in love and two, that we all unite to fight against the hatred that killed her. Hate doesn’t have a creed, race or religion, it is poisonous,” he said. “Jo would have no regrets about her life, she lived every day of it to the full.”

Indeed, Ms Cox’s maiden speech to parliament was hopeful and remarked on how much unites her constituents.

Ms Cox became Labour MP for Batley and Spen at last year’s General Election. The mum of two was widely respected in the Commons for her campaign work and last October launched the All Party Parliamentary Friends of Syria Group.

She abstained in the vote on whether to extend RAF bombing raids against IS to the war-torn country.

A cross party vigil was held in Parliament by the leader of the Labour Party, Jeremy Corbyn, who called Mr Cox’s statement “beautiful and moving” in a speech to those who gathered.

The astonishing attack comes six years after Labour MP Stephen Timms was stabbed twice at a constituency surgery in revenge for his vote for the Iraq War. He thought Roshonara Choudry wanted to shake his hand when she smiled before lunging at him in Newham, East London.

The whole of the Labour family, and indeed the whole country, is in shock and grief at the horrific murder of Jo Cox pic.twitter.com/obic5pOCS3 — Jeremy Corbyn MP (@jeremycorbyn) June 16, 2016

Absolutely sickened to hear of the assassination of Jo Cox. She was young, courageous, and hardworking. A rising star, mother, and wife. — Gabrielle Giffords (@GabbyGiffords) June 16, 2016

Ms Cox supported Corbyn in the Labour leadership battle though later wrote in the Guardian that she regretted backing him and ended up voting for ‘Blairite’ Liz Kendall.

Prior to becoming an MP she worked as head of policy for Oxfam, and was an adviser to Sarah Brown and Baroness Kinnock.

Prime Minister Malcolm Turnbull has also tweeted a condolence message saying he was deeply shocked by the murder of Ms Cox.