Laura Davies, who is the Labour candidate for the Shrewsbury & Atcham parliamentary seat, posted a copy of the letter, which was sent to her home, on Twitter.

The letter addresses Dr Davies in abusive terms and threatens her with being tied up and having rocks thrown at her.

It also accuses her of being dishonest.

She tweeted: "I’m not sure whether to be amused or intimidated by this. Worrying that they have my home address though..."

Dr Davies confirmed she had contacted police about the letter, and said it was illustrative of the current discourse around political differences.

She said: "It is symptomatic of the public discourse around politics.

"We put ourselves out there and subject ourselves to this level of scrutiny, quite rightly because the public should scrutinise their wannabe public representatives – and we expect a degree of criticism, but politicians or candidates should not expect to feel intimidated or receive threatening letters."

Shrewsbury's Labour Party tweeted its support for Dr Davies, saying: "We are disgusted to see this intimidating and threatening letter sent to @lauraforshrews and stand 100 per cent against such behaviour. Use of (threats of/) violence to suppress political activity or views is absolutely unacceptable in any circumstances."