A corporal in the British Army issued a death threat to a Labour MP and appeared to incite "civil war" on Twitter on Wednesday afternoon.

The corporal, whose Twitter account has now been deleted, wrote to Rayner: "Ohh fuck off you stupid bitch" and said the MP would "perish when civil war comes and it’s coming". The soldier ended the tweet by adding that "17.4 million people are gunning for blood if we don’t leave".

The Ministry of Defence confirmed to the New Statesman this morning that the corporal “is a serving member of the Armed Forces".

However, the MoD did not say that it would investigate the tweet, saying instead that it “has been referred to the civilian authorities to investigate." A spokesperson added: “The Army is a politically neutral organisation and holds its people to the highest standards.”

The tweet was sent in response to Rayner's condemnation of comments made on Monday by the Attorney General, Geoffrey Cox, describing parliament as "dead" and a "disgrace" for refusing to offer his party an early general election. Rayner shared a screenshot of the reply from the corporal, describing it as an example of the "usual vile tweet I get daily".

Another statement made by the same soldier on social media described Jo Swinson as “dangerous" and threatened that the Liberal Democrats' position on Brexit could lead to “civil war". A comment made under the corporal's name on the UK Defence Journal website argued that migrants should be sent back to their home countries because they "try impose their way of life into us”.

The British Army has come under increasing scrutiny to do more in the face of right-wing extremism in recent years, following a number of incidents involving service members. In May, the army released a leaflet entitled “Extreme Right Wing (XRW) Indicators & Warnings” to help alert defence staff to soldiers who show signs of extremism. The army was also forced to discipline troops when footage emerged showing soldiers in Afghanistan using a picture of Jeremy Corbyn for target practice. At the time, the Ministry of Defence said the video was "not fitting of the high standards we expect”.

On the same evening that the corporal's tweet was sent the MP for Dewsbury, Paula Sherriff, asked Boris Johnson to moderate his rhetoric after he described parliament's opposition to a no-deal Brexit as a "surrender" that would "betray the people". Sherriff protested that such language endangers MPs such as herself who are "subject to death threats and abuse every single day”.

The Prime Minister responded: "I have never heard such humbug in all my life”.