UK special forces officers raised concerns of “questionable behaviour” by certain units in Afghanistan, describing alleged unlawful killings as “massacres”.

In email exchanges, which were read to an independent inquiry on Monday, some officers feared being “dragged down” with the units carrying out the killings “when the next WikiLeaks occurs”.

One officer, who like all others had their identity hidden in the interests of national security, questioned a “rash of curtain-shootings”, which involved UK special forces taking suspected insurgents back into compounds before they then returned with a weapon from behind a curtain.

In an email chain concerning a night raid on February 9 2011, in which eight people were killed, one special forces officer said there appeared to be a “casual disregard for life”, after another officer said the spate of curtain-shootings were as if they were “setting the conditions for their execution”.

One email read: “And finally they shot a guy who was hiding in a bush who had a grenade in his hands. You couldn’t MAKE IT UP.”

In his opening submissions at the Royal Courts of Justice, counsel to the inquiry Oliver Glasgow KC said UK special forces allegedly had a policy of executing males of “fighting age” who posed no threat.

Mr Glasgow said one senior officer queried whether “deliberate policy was being demonstrated where all fighting-aged males in a given scenario were killed irrespective of whether they posed a threat or not.”

In a conversation the senior officer had had with another, the inquiry heard a second officer had received “disturbing information” that could have a “detrimental effect on the possible reputation of the UK special forces”

The second officer issued a statement on March 24 2011, in which he said a soldier “implied that photos would be taken of the deceased alongside weapons that the ‘fighting-age male’ may not have had in their position when they were killed.”

The central allegation of the inquiry, which will focus on alleged illegal activity in the war-torn country between 2010 and 2013, is that special forces “abused” night raids to carry out the policy.

Mr Glasgow also said there were claims that Afghan partner units (APU) “refused to serve with UK special forces due to their behaviour”.

Emails exchanged between two officers about a night raid on February 16 2011 showed that an APU had complained to a commanding officer that “no-one was firing” at the special unit before four men were killed.

In the email chain, the officer said the APU saw “this as confirmation that innocents were killed”.

In one email, the officer said: “I explained that there was intelligence to suggest involvement in insurgency and that was the basis for the operation – this was not well received.

“He said that they are teachers and farmers and that they have weapons for self-protection, but they are emphatically not Taliban.

“He suggested that the houses were used as guest houses, and that the villagers have no option but to house them.”

An email from a member of the special forces legal team suggested that they had made comments about the February 16 raid that “public interest lawyers may undoubtedly raise in the inevitable public inquiries”.

An exchange between two special forces officers about the deliberate detention operation (DDO) suggested “questionable behaviour” but certain units had been “gathering momentum”.

One email read: “Why are we the only ones who see this bollocks for what it is?

“(A commander) is keen to threaten people when disclosure is breached – not that anything EVER comes of it – and here he has serious amount of questionable behaviour from his (special forces unit) that is gathering momentum.”

The inquiry will look at allegations that “numerous” killings were carried out, as well as the alleged cover-up of illegal activity and inadequate investigations by the Royal Military Police (RMP).

It was launched in the wake of legal challenges to the Government by Leigh Day solicitors on behalf of the Saifullah and Noorzai families, as well as a number of significant media investigations.

Mr Glasgow read out another email chain between two special forces officers, concerning the February 16 night raid, which read: “Is this about (a special forces unit’s) latest massacre! I’ve heard a couple of rumours.”

The second officer replied: “Yeah mate… for what must be the 10th time in the last two weeks, when they sent a (suspect) back into the (room) to open the curtains (??) he re-appeared with an AK.

“Then when they walked back in to a different (room) with another (suspect) to open the curtains he grabbed a grenade from behind a curtain and threw it at the (special forces soldiers).

“Fortunately it didn’t go off…. this is the 8th time this has happened.

“And finally they shot a guy who was hiding in a bush who had a grenade in his hands. You couldn’t MAKE IT UP.”

Mr Glasgow said there were claims in a “restricted security compartment”, which were recovered years later, that there were details of a conversation with a soldier who allegedly “admitted there was a policy in special forces to kill fighting-age males”.

Two RMP investigations, codenamed Operation Northmoor and Operation Cestro, will be scrutinised by the inquiry.

No charges were brought under Operation Northmoor – a £10 million investigation which was set up in 2014 to examine allegations of executions by special forces, including those of children.

Operation Cestro saw three soldiers referred to the Service Prosecuting Authority, but none were prosecuted.

The inquiry will now hear submissions on behalf of the families of 33 people, including eight children, who were allegedly killed by special forces.

The independent statutory inquiry was commissioned by then-defence secretary Ben Wallace under the 2005 Inquiries Act.

A Ministry of Defence (MoD) spokesman said: “The MoD is fully committed to supporting the inquiry as it continues its work.

“It is not appropriate for us to comment on allegations which may be within the scope of the statutory inquiry and it is up to the statutory inquiry team, led by Lord Justice Haddon-Cave, to determine which allegations are investigated.”