The Ministry of Defence has launched an investigation into a video which appears to show soldiers firing shots at a picture of Jeremy Corbyn.
The video, which has not been verified by the BBC, appears to show four paratroopers using a portrait of the Labour leader for target practice.
An Army spokesperson said it was aware of the video and was investigating.
“This behaviour is totally unacceptable and falls well below the high standards the Army expects,” they said.
A Labour Party spokesman called the behaviour alarming and unacceptable but said they have confidence in the Ministry of Defence to investigate and act on this incident.
Conservative MP Tom Tugendhat, a former lieutenant colonel who served in Iraq and Afghanistan, said the video was “disgraceful”.
Rory Stewart, Conservative minister for prisons, told the BBC’s Victoria Derbyshire that it was “completely wrong” and was “outrageous behaviour”.
“They should not be political – they are there to defend the country and the Queen,” he said.
The emergence of the video comes at a time of heightened alarm about the safety of MPs as tensions rise over Brexit.
Labour MP Jess Phillips tweeted: “This is absolutely hideous and irresponsible under this or any climate.”
And Angela Rayner, Labour’s shadow education secretary, said she hoped the investigation would be conducted “thoroughly and the conclusions made public”.
It is not known when the footage was filmed but it is thought it was recorded in Kabul, Afghanistan.
It is believed the short clip first circulated on Snapchat before being posted on Twitter.
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