Jon Snow introduces Sri Lanka's Killing Fields, 'one of the most important stories' he had ever reported (still taken from Channel 4 footage)
The documentary, which was shown on Channel 4 in June and was said to show "executions, atrocities and the shelling of civilians", prompted the Foreign Office to repeat calls for an independent investigation of alleged war crimes during the 2009 military operation in Sri Lanka.
At the time the film was described by presenter Jon Snow as "one of the most important" stories he had ever reported, and one of the most shocking ever screened on Channel 4.
In its broadcast bulletin published today, Ofcom said it found the documentary did not breach Rule 5.5 on due impartiality, Rule 2.2 on misleading material or Rule 2.3 on offensive material.
Concluding its findings on the issue of impartiality the regulator noted that Channel 4 did offer the Sri Lankan government a right to reply, including its response in the programme.
Ofcom added that the programme also included a number of official statements previously made by the Sri Lankan government on the events.
The regulator also responded to accusations that the programme focussed more on the Sri Lankan government than other groups.
"While the subject matter did present evidence which predominantly covered the actions of the Sri Lankan government offensive, the documentary included explicit references to the LTTE [Liberation Tigers of Tamil Eelam] activities at this time where this was relevant.
"Ofcom therefore concluded that overall Channel 4 preserved due impartiality in its examination of the Sri Lankan government's actions and policies during its offensive".
The broadcaster also "categorically rejected any suggestion that the material was faked or manipulated", and the programme did refer to such allegations by the Sri Lankan government.
"Channel 4 explained that great care was taken to verify all of the material received before it was broadcast in order not to mislead the audience, and the audience were advised of the expert assistance obtained to ensure the material had not been manipulated.
"... It is Ofcom's view that the broadcaster therefore ensured that the audience was not materially misled regarding the nature of the content by taking reasonable steps before the broadcast to establish that the material was not faked or manipulated, and informing the audience of those steps during the programme."
Finally, Ofcom ruled that warnings given by Channel 4 regarding potentially offensive images "were explicit and helped provide viewers with the information to decide if they wished to continue to view".
"Channel 4 has a unique public service remit to provide programming that is challenging, diverse and likely to provoke debate.
"Consequently, the broadcaster has a history of broadcasting very challenging material from war zones (including graphic footage) and seeking out the voices and views of those who may not be represented.
"The images included in this programme, whilst brutal and shocking, would not have exceeded the expectations of the audience for this Channel 4 documentary scheduled well after the watershed with very clear warnings about the nature of the content."
In a statement Dorothy Byrne, head of news and current affairs at Channel 4 says the broadcaster is "delighted with this unqualified vindication on all counts".
"The finding is testament to the rigorous journalistic methods employed by ITN Productions and the meticulous legal and compliance scrutiny involved to ensure this vital film – which presented devastating prima facie evidence of war crimes and crimes against humanity – could be broadcast."
According to Channel 4 the film has been watched by over a million viewers in the UK.