Video report by ITV News Political Correspondent Angus Walker
MPs are being warned not to go out campaigning alone in the dark, and one has even been advised not to drive alone, as threats and abuse continue to pile up.
In the past week, Tory MPs Caroline Spelman and Nicky Morgan, former Labour MP Louise Ellman and Liberal Democrat MP Heidi Allen have all cited abuse as part of their decision not to run in the general election.
On Thursday, Change UK leader Anna Soubry shared two threatening letters she received with ITV News, with one warning "Cox was first and you're next, you treacherous, worthless f****** dead sl**".
Labour MP Rosie Duffield, meanwhile, told ITV News police have warned MPs not to go out campaigning alone in the dark.
She said it was the "kind of advice that really restricts our campaigning, so not going out alone, not going out in the dark.
"Those are all necessary unfortunately at the moment but it does make a winter campaign very difficult to conduct."
She added: "I suppose it is shocking but actually we are used to that now, it's just part of our everyday lives."
ITV News Political Correspondent Paul Brand on the affect the abuse can ultimately have on democracy
The specialist unit dealing with MPs' security based at Scotland Yard is now assessing the threat during this General Election campaign which will see an unprecedented police-led focus on protecting candidates.
In a statement given to ITV News, the Met Police said it's working with forces around the country to ensure effective security measures are in place.
These will be continually reviewed in the run-up to the election and allegations of abuse of intimidation will be treated very seriously
Offenders, they say, will be pursued relentlessly.
In clear criticism of Grant Shapps's comments earlier on Thursday that MPs should simply "not read" online abuse, Anna Soubry shared two examples of shocking threats sent to her.
The leader of Change UK tagged Mr Shapps in a tweet in which she shared an image of a condolence card sent to her partner, warning his "treasonous" partner will "be gone very soon".
ITV News has blurred some of the more offensive words.
In another post, Ms Soubry shared a letter delivered to her office, calling her "treacherous" and "worthless".
"Cox was first," it says, referring to murdered Labour MP Jo Cox.
She said in her tweet, which again tags Mr Shapps: "[It's] difficult for my team & I not to read death threats sent in a letter.
"Maybe offenders should warn on envelope 'offensive contents'.
"But most threats come to my MP email account.
"Difficult not to read your emails.
"Stop blaming the victim & start taking this seriously."
Having repeated threats sent to her has made Ms Soubry more cautious about holding drop-in sessions.
"You don't know who might turn up," she told ITV News.
"That is the problem and that's why so many of us have been really reluctant to do what we used to do these sort of open drop-in surgeries."
Jo Cox Foundation attacks 'abhorrent' abuse
Also on Thursday, foundation set up in the name of Ms Cox attacked the "abhorrent" abuse aimed at female MPs.
Catherine Anderson, chief executive of the Jo Cox Foundation, said: "One of Jo's great passions was encouraging more women to come forward as candidates, so it is very sad to see talented women standing down at this time."
She added that "while abuse and intimidation directed at those in public life is always abhorrent", evidence collected by the foundation showed "women are disproportionately more likely to be targets".
"We all have a responsibility to call out threats and unacceptable behaviour, whether online or offline," she said.
There are currently 649 MPs, of whom 211 are women.
As of Thursday morning, a total of 17 female MPs and 41 male MPs have stood down ahead of the general election on December 12.
An Amnesty International report in December 2018 found that 7.1% of tweets to female journalists and politicians in a study of 228,000 tweets contained abusive or problematic language.
Chiara Capraro, Amnesty's women's rights programme manager, said: "Our research has shown the shocking levels of abuse on Twitter that is hurled against women in politics - including death and rape threats - and the chilling effect this can have on their lives.
"We shouldn't be seeing women politicians feel the need to self-censor, leave social media or even quit politics altogether because of the dangerous abuse they receive.
"The run-up to an election can be a particularly difficult time, with levels of abuse often skyrocketing ... social media companies must do far more to combat this extremely worrying trend, so that women can feel safe to participate in public debate and politics."