Music teacher Carla Hales thought she had been stabbed.

Key points: Abuse against Members of Parliament is on the rise in the UK

Abuse against Members of Parliament is on the rise in the UK 18 female MPs are standing down at the upcoming election

18 female MPs are standing down at the upcoming election Labour MP Jo Cox was murdered in 2016

She had just finished taking photographs outside the picturesque Bourne Mill in Colchester, Essex, and was looking at her phone when the first blow came.

By the time she looked up the male assailant was running away.

"He punched me three times in the sort-of side in the ribs," she told the ABC.

"It hurt and for a horrible fraction of a second I thought 'oh my God, I have been stabbed'."

Just prior to the attack, Carla had been leafleting for a local council election, where she was running for the Conservative Party.

She was bruised but later cleared to go home by local hospital staff.

Music teacher Carla Hales stood as a Conservative candidate in local council elections. ( ABC News: Tim Stevens )

On that occasion in April, she wasn't elected and the offender was never found, although police suspect the attack was politically motivated.

"I had never experienced that sort of violence in the town at all," she said.

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"You know, I have a husband and I have a job and I'm just a normal person."

The attack has prompted her to carry a personal alarm in her handbag.

"It shouldn't be like that, it never should be like that."

Carla Hales is one of the growing number of women in the British political system at the frontline of vitriolic abuse that extends from the very top down.

An increase in death threats and threats of sexual violence has led police to warn candidates in the upcoming December general election to not campaign alone or in the dark.

In some cases female MPs have been told to install panic buttons in their homes.

Luciana Berger, who defected from the Labour Party to the Liberal Democrats, knows too well the risks of public life.

She has seen six people convicted for harassment and threats directed at her and her family, with two of those convicted sent to prison.

MP Luciana Berger now avoids advertising where she will be in advance. ( AP: Kirsty Wigglesworth )

This year, she was sent death threats, with one message telling her she would get it "like Jo Cox did".

Labour MP Jo Cox was stabbed and shot to death by a Nazi-obsessed 53-year-old man after a public meeting in her constituency in 2016, a week before the EU referendum.

"It has presented itself in lots of different ways, via email, online, on Twitter, on social media, on blogs, in person, to my face, abusive phone calls to my office — unfortunately you name it, I have seen it," Ms Burger told the ABC outside the Palace of Westminster.

"I do things very differently today than I did back when I was first elected nine years ago. Simple things like not advertising where I'll be in advance."

While not the only factor, the polarising debate over Brexit has seen the abuse of Members of Parliament skyrocket.

According to police, the number of crimes against MPs doubled between 2017 and 2018.

"It's becoming more toxic, it is becoming more vitriolic," Mandu Reid, the leader or the Women's Equality Party told the ABC.

She said women were at the sharp end of the abuse.

Mandu Reid is the leader of the Women's Equality Party. ( ABC News: Tim Stevens )

"There's very often a sexual nature to it, rape threats, the severity and aggression behind some of the death threats aren't necessarily replicated in the same way when you examine the abuse that men in public life receive," she said.

She said the severity of the abuse was the same regardless of which side of the Brexit debate the political figure falls.

"It should be treated as a national scandal," Ms Reid said.

Catherine Anderson, CEO of the Jo Cox Foundation, which was established after the Labour MP's murder, said since her death the security situation for politicians had become worse, not better.

"We know of councillors in London who have had their cars burned, a couple of candidates in the local elections who had their cars driven off the road," Ms Anderson said.

"It's really a toxic environment that people in public life are operating in."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 41 seconds 41 s Husband of late MP Jo Cox warns against inflammatory rhetoric

It is a toxicity many of the 18 women who have decided to bow out of politics before the December poll are citing as part of their reason for leaving.

Fifty members from all parties won't recontest their seats, but Ms Reid said the trend for women was concerning.

"The women who've announced that they're stepping down at this election, many of them are citing abuse as a key factor in that, have on average served for nine years, the men on average 20 years," she said.

"That tells you something is going on which is resulting in women, some of the brilliant women who've served in Cabinet, not fulfilling their potential."

Luciana Burger said stepping down had "certainly crossed her mind" after years of threats and anti-Semitic abuse.

"I have every sympathy with those colleagues of mine who decided that they are not going to stand again," she said.

Charlotte Hoagland is one woman hoping to enter the fractured political fray and is running as a candidate for the Liberal Democrats.

"Basically, I was told that I should introduce myself to the local police constabulary," she said.

"I think it is very worrying that people are having to have these ways of protecting yourself because you are out there to talk to people and you shouldn't have to worry for your safety."

A police directive not to campaign in the dark is difficult for a December election when the sun begins to set in the UK well before 4pm.

"When I campaign with my team I make sure that everyone is in groups of male and females and we have plenty of flashlights," Ms Hoagland said of the personal measures she is taking to protect herself.

Former Conservative MP Anna Soubry, who has faced a string of abuse, this month had a card posted to her that read "Jo Cox was first, you are next".

Another letter to her 85-year-old mother said: "We know where you are, we are coming to get you."

Sorry, this video has expired The number of protesters outside the Houses of Parliament has grown post-Christmas, Samantha Hawley says.

Ms Soubry was also harassed outside the Parliament earlier this year and called a "Nazi".

The offender was charged and received a suspended jail term.

Carla Hales has decided to run again as a candidate in the local elections next year, and says she thinks she can do a good job representing her community.

But she will take a more cautious approach to campaigning.

"I will be out more in the day and early evening and I will always go out with a pair — with my husband or a colleague."