The father of a Marine shot dead by a teenager and alleged sex slave in Afghanistan has slammed the US military for making him seem like an enemy to abused local children.

According to Gregory Buckley Sr, American officers were ordered to turn a blind eye to the sexual abuse of Afghan boys - even on military bases - because that was not the 'priority of the mission'.

It was this policy, he believes, that led to his son Lance Corporal Gregory Buckley Jr, 21, being gunned down on Helmland Province in 2012 by 17-year-old Aynoddin, an Afghan 'tea boy' for local police chief Sarwar Jan - who had previously been reprimanded for child abduction.

'As far as the young boys are concerned, the Marines are allowing it to happen and so they’re guilty by association,' Buckley Sr told the New York Times. 'They don’t know our Marines are sick to their stomachs.'

His words come as he files a landmark lawsuit against the military, with testimony from US Marines, describing how local boys would be chained to beds and abused daily by America-backed Afghan officers - but they were barred from intervening.

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Gregory Buckley Sr, left, who believes his son Lance Corporal Gregory Buckley Jr, right, believes the policy of turning a blind eye to sexual abuse was a factor in his son's death

Lance Corporal Buckley was gunned down in the gym at the Forward Operating Base Delhi, in Afghanistan's Helmand province in August 2012, by a 17-year-old Afghan

One officer, Dan Quinn, was even discharged for beating up a commander who allegedly chained a boy to a bed, raped him multiple times, then beat up his mother when she tried to save her son.

And two other officers, Major Jason Brezler and Charles Martland, claim they are earmarked for forcible retirement because they flagged the issue of child sex abuse.

According to Pentagon policy, sexual abuse is deemed a local concern for the Afghan Local Police unless it is deemed to be an act of war.

'My son said that his officers told him to look the other way because it’s their culture,' Buckley Sr told the Times.

He claims it was the last thing they ever spoke about over the phone before his death.

'At night we can hear them screaming, but we’re not allowed to do anything about it,' Buckley remembers him saying.

And now he is convinced that his son's killing may have occurred because of the alleged sexual abuse by the Afghan police chief, who was an ally to America.

Buckley Jr, from Long Island, New York, was one of three officers gunned down by Aynoddin, armed with an AK-47, while they worked out in the gym at Forward Operating Base Delhi, in Afghanistan's Helmand province on August 10, 2012.

It was later revealed that the teen may have been one of the sex slaves that Jan supposedly brought onto the base. He was not vetted and later talked about killing the soldiers in the name of Jihad.

Jan had been arrested by Afghan police in 2010 for child abduction and support for the Taliban, according to the Times. By 2012, he had been appointed police commander at Forward Operating Base Delhi. It is not clear how or if he was reprimanded and how he came to be appointed.

Lance Corporal Buckley was just 21 years old when he died. His funeral took place in his home of New York

Mr Buckley, centre, at his son's funeral. He claims his son told him in one of his final phone calls home, that officers said Marines were to 'look the other way' in regards to abuse because it is 'Afghan culture'

Before the attack, fellow Marine Major Jason Brezler, left, warned his comrades stationed overseas about police chief Sanwar Jan's, right, background in an email noting he was a child abuser

As he was drawing up the lawsuit last year, Buckley told Fox News: '[Aynoddin] shot my son point blank with an AK-47. Shot him four times in his chest and once in his neck.

'He was in the gym with a pair of shorts and a tank top on. How is that allowed?

'I want them to admit that they were wrong. And I want someone to be held responsible for my son's death.'

Before the attack, fellow Marine Major Jason Brezler warned his comrades stationed overseas about Jan's background in an email.

He reported that Jan was a noted child abuser and there were allegations he sexually abused minors on U.S. bases in the past.

However, Brezler was subsequently honorably discharged for sending the email from his personal, unsecured, Yahoo account.

It comes as another decorated soldier who had worked for the U.S. Army Special Forces for 11 years is being discharged after claims he stood up for a young rape victim and his beaten mother in Afghanistan.

Sergeant 1st Class Charles Martland, 33, was serving in the country's war-torn Kunduz Province in 2011 when he apparently learned an Afghan police commander he had trained had raped a boy.

He and his team leader, Daniel Quinn, confronted Officer Abdul Rahman - who had also allegedly beaten the 12-year-old's mother for reporting the sexual assault - and 'shoved him to the ground'.

U.S. Army Special Forces Sergeant 1st Class Charles Martland, who is being discharged over claims he stood up for a young rape victim and his beaten mother in Afghanistan

Despite Rahman walking away only bruised, Martland and Quinn were disciplined.

The Army reportedly halted their mission, put them in temporary jobs, and then, finally, sent them home.

Upon their return, Quinn quit the Army and is said to have secured a job on Wall Street.

However, Martland, from Massachusetts, launched a fight to remain a Green Beret.

But now, the dedicated soldier has been 'involuntary discharged' from the Army following a 'Qualitative Management Program' that was apparently carried out in February this year.

Buckley Sr's lawsuit accuses the Marine Corps, Department of Defense, the Navy, the U.S. Naval Criminal Investigative Service and former Marine Corps Commandant General James Amos of withholding the full truth surrounding his son's death.

Asked about the sexual assault of young Afghan boys, whether the current policy is under review and why US military personnel are being told turn a blind eye, White House Press Secretary Josh Earnest read the following statement:

‘The United States is deeply concerned about the safety and welfare of Afghan boys who may be exploited by members of the Afghan national security and defense forces. This form of sexual exploitation violates Afghan law and Afghanistan's international obligations.

‘More broadly, protecting human rights, including by countering the exploitation of children, is a high priority for the US government. We monitor such atrocities closely and continually stood up for those who suffered exploitation and a denial of basic human freedoms.

‘The United States works closely with the Afghan government, civil society and international organizations in Afghanistan to put an end to the exploitation of children, but also to incorporate human rights training into our law enforcement programs to heighten awareness in prosecution of such crimes.

‘We continue to encourage the Afghan government and civil society to protect and support victims and their families, while also strongly encouraging justice and accountability under Afghan law for offenders.'

Asked if the president – the nation’s Commander-in-Chief of the armed services - would tell a military leader to intervene if he sexual assault happening, Earnest declined to provide a direct answer.

‘For the policies that sort of govern the relationship between US military personnel serving in Afghanistan and their Afghan counterparts, I'd refer you to the Department of Defense,’ he said, adding that the statement he read aloud ‘indicates just how seriously we take this issue and how this this kind of behavior.’

It ‘doesn't just violate Afghan law, and Afghanistan's international obligations, but it certainly violates, I think, pretty much everybody’s notion of what acceptable behavior is,’ he said.

Pressed to explain the circumstances in which US military personnel would allow assault to happen on their watch, Earnest again dodged. ‘For the rules of engagement and the kind of structure that's in place,’ contact DOD, he said.

Asked point blank later in the briefing if the president is ‘tolerating’ sexual assault of women and children abroad and is ‘acceding’ to the policy that his military advisers at the Pentagon have established - not to intervene in crimes unless they are an act of war – Earnest deflected once again, invoking the Defense Department. He said he would not answer questions ‘about a policy that governs the conduct of US military personnel in a dangerous place.’