Norfolk election candidates from across political lines have spoken of the 'demoralising' effect of the 'aggression and abuse' they face while on the campaign trail.

Political hopefuls and former MPs alike have spoken out about the "worrying" issue, after police confirmed they were investigating an alleged shooting threat made to the Liberal Democrat candidate Steffan Aquarone in Mid Norfolk.

Mr Aquarone said a man told him he would shoot him if he was successfully elected, while he was campaigning on Wednesday.

He later said the man had apologised to him and added: "Peace comes from our ability to resolve conflict."

READ MORE: 'I would shoot you': Election candidate's death threat shock

But widespread concern over the issue comes after the launch of a national police operation to protect election candidates, prompted by widespread reports of threats, abuse and harassment towards MPs and politicians, with campaigners warned against canvassing alone or after dark.

Norwich North Conservative candidate Chloe Smith warned the issue of abuse could discourage people from standing for election.

"It can put people off from becoming involved in public service," Ms Smith said.

"Nobody should have to put up with intimidation, threats or violence while we go about a peaceful democratic election."

She added: "I have experienced abuse in Norwich from the left in the 2015 election and in 2017.

"It is not driven by or only about Brexit. It has changed a little - people can expect it online rather than only on the streets."

Ms Smith said incidents she had experienced included someone "shouting and screaming and abusing me" at an event in 2017, which she reported to the police, as well as being "chased through an underground car park".

She added: "That's just not acceptable. It's a really ugly side of the left in Norwich.

"We are being very clear with volunteers and activists about how to stay safe on the campaign."

Politicians including Harriet Harman and Hillary Clinton have warned about the impact of abuse and attacks, with fears about threats on the rise since the 2016 murder of the Labour MP Jo Cox ahead of the Brexit referendum.

READ MORE: City politician speaks out after Labour campaigners reportedly abused on campaign trail

Several high profile female MPs said they would not be standing in the election on December 12, with cabinet minister Nicky Morgan and former Conservative MP Heidi Allen citing intimidation and abuse as the cause.

Labour candidate in Broadland, Jess Barnard, described the rise in aggression as "worrying".

"There does seem to be an increasing community of people who are just so frustrated and have so much anger," she said

"There have been a number of incidents of aggression and in some cases violence in Norfolk against Labour members.

"People should be free and feel safe to go out and campaign for their local party and canvass without having to fear physical or vernal aggression.

"It is quite worrying. I have experienced verbal abuse on the doorstep in Norwich and in Peterborough and my partner has been on the end of quite serious verbal threats."

Parties have taken steps to help candidates ensure their safety on the campaign trail, with Labour activists in Norfolk encouraged to canvass in tight-knit groups, with activists staying within eyesight.

But Karen Davis, Labour candidate in Norwich North, previously said canvassers had been threatened with violence while doorknocking in Sprowston in September.

One activist was reportedly told: "You have three seconds to get out of here before I hit you."

Police said the allegations were being investigated at the time.

And in April this year, the Labour candidate Cathy Cordiner-Achenbach, who was standing in May's borough council election, was punched while delivering leaflets in Great Yarmouth.

Police investigated the assault.

However, South Norfolk Green Party candidate Ben Price said he felt the rise in aggression came from a lack of trust in politicians.

"People have been let down by national politicians a lot," he said.

"They feel they're not really being listened to. That trust is being broken down [and] that comes back on the doorstep."

But he described the spike in female politicians standing down as a result of threats and abuse as "a terrible shame".

Mr Price added: "We have to be really wary safeguarding-wise.

"I have received real aggression and abuse from residents. It does affect you and it does demoralise you and play on your mind."

He said if he were knocking on doors in a block of flats, he would "go to the door furthest from the exit first, so you're not blocking your exit from the building".

READ MORE: Unity across party lines after council candidate is punched on election trail