Jeremy Corbyn said he was "shocked" that paratroopers in Afghanistan used an image of his face for target practice.
The Ministry of Defence (MOD) has launched an investigation into the conduct of the personnel from 3rd Battalion, Parachute Regiment, who were filmed in Kabul shooting at a picture of the Labour leader.
Mr Corbyn said: "I'm shocked, obviously, that this sort of thing has happened.
"I hope the Ministry of Defence will conduct an inquiry into it and find out what was going on and who did that."
The video, which was uploaded to Snapchat, had a graphic saying "happy with that" across the screen throughout and a number of marks can be seen peppered across Mr Corbyn's face.
The rounds used in the video are 'simunition' paint rounds, which are low velocity and can be used at short range.
Forces News has chosen to blur the faces of those involved.
Around 400 soldiers from 16 Air Assault Brigade, of which 3 PARA is part, are deployed to Afghanistan on force protection duties, working with NATO and Afghan partners.
The Prime Minister's official spokesman said on Wednesday:
"This is clearly unacceptable. The MOD are now conducting a full investigation."
Shadow Defence Secretary Nia Griffith wrote to the Defence Secretary Gavin Williamson asking him to condemn the video footage "immediately".
The Defence Secretary responded by commending the "prompt and clear leadership shown" by the Army investigating the incident, and describing the video footage as "completely unacceptable".
A Labour Party spokesman said: "This behaviour is alarming and unacceptable. We have confidence in the Ministry of Defence to investigate and act on this incident."
Labour's Shadow Armed Forces Minister, Wayne David, echoed the comments saying he was "appalled" and "disgusted" by the actions of the individuals, adding:
"It sent out a violent, horrific message and I don't think that is represented in our Armed Forces - I know they're not like that."
Shadow Armed Forces Minister 'appalled' at target practice footage
Mr David is now calling on the Defence Secretary to make sure it can never happen again.
Commander of 16 Air Assault Brigade, Brigadier Nick Perry, said the Army is conducting a full investigation, is keen to get to the bottom of the incident, and is "obviously taking this extremely seriously".
"The video shows totally unacceptable behaviour and a serious error of judgment that falls far below the behaviour that we expect of our soldiers in the brigade," he added.
Brigadier Nick Perry: Target practice incident a 'serious error of judgement'
An Army spokesperson said: "We are aware of a video circulating on social media.
"This behaviour is totally unacceptable and falls well below the high standards the Army expects.
"A full investigation has been launched."