Wounded civilian
This photograph released by the pro-Tamil rebel website TamilNet.com shows a civilian wounded by shelling at a makeshift field hospital in Mullivaikal.

Britain has renewed calls for Sri Lanka to investigate allegations of war crimes after video footage apparently showing the summary execution of naked and bound prisoners was broadcast on UK television, in the documentary SriLanka's Killing Field.

The film, shown on Channel 4, reportedly shows "trophy videos" taken on mobile phones by Sri Lankan soldiers taking part in the military operation in 2009 to crush the Tamil Tiger insurgency and end a 25-year civil war.

The documentary contained extremely violent scenes and included footage of apparent extrajudicial killing of prisoners by government forces, the aftermath of targeted shelling of civilian hospitals and the bodies of female Tamil fighters who appear to have been sexually assaulted.

As the team behind the film refused for the film to be one sided, they also reviewed atrocities carried out by the Tamil Tigers including the use of human shields and a suicide bombing in a government centre for the displaced.

Sri Lanka's civil war ended in 2009, as the Colombo government claimed victory over the insurgents after a bloody military operation that killed thousands of people and displaced many more.

Army and Tamil separatists fought a long conflict involving air raids, roadside blasts, suicide bombings, land and sea battles. The war originally started in 1983 and more than 80 000 people have allegedly died.

While there is a long-established Tamil minority in the north and east, during colonisation by the British, the latter brought Tamil labourers to work the coffee and tea plantations in the central highlands, making the island a major tea producer.

The majority Buddhist Sinhalese community responded badly to what they understood to be favouritism and tensions between the two groups started to raise.

Independence saw the assertion of Sinhala nationalism which further deepened ethnic division until civil war erupted in the 1980s between Tamils pressing for self-rule and the government.

While most of the fighting took place in the north, the conflict also spread further in the country as Tamil Tiger rebels carried out suicide bombings in Colombo in the 1990s.

International concern was raised about the fate of civilians caught up in the conflict zone during the final stages of the war. More than 250 000 Tamil ended up in refugees camps for months while allegations that the government had ordered the execution of captured or surrendering rebels also surfaced.

The Channel 4 documentary comes as a panel of experts convened by the United Nations secretary general, Ban Ki-moon, reported this year that it had found "credible allegations" of war crimes on both sides and said that a civilian death toll of 40,000 or more could not be ruled out.

However, Sri Lankan authorities rejected the footage as falsified and accused the United Nations of bias and jumping to hasty conclusions.

In 2010, in its annual human rights report, the Foreign Office said it remained concerned about continued human rights violations, disappearances, extrajudicial killings and arbitrary arrests in the country after the end of the war.

Responding to the film, Foreign Office minister Alistair Burt said: "The recent UN panel of experts' report, this documentary and previously authenticated Channel 4 footage constitute convincing evidence of violations of international humanitarian and human rights law.

"The whole of the international community will expect the Sri Lankans to give a serious and full response to this evidence.

"Since the end of the conflict the UK has called for an independent, thorough and credible investigation of the allegations that war crimes were committed during the hostilities and the UK government expects to see progress by the end of the year. I reiterated this message to the Sri Lankan foreign minister on 14 June.

"If the Sri Lankan government does not respond we will support the international community in revisiting all options available to press the Sri Lankan government to fulfil its obligations.

"Unless this is done, Sri Lanka will not be able to move on, and the prospects for reconciliation between Sri Lanka's communities will be curtailed. It is of the greatest importance that this does not happen."

Meanwhile, the Home Office was still preparing to deport some 40 Tamils to the south Asian island state, including five who claim that their safety has been put in danger after UK officials passed papers in their case to the authorities in Colombo.

While human rights campaigners insist the refugees are at risks of reprisals and should not be sent back to the Island, and despite the broadcast of the programme, it seems unlikely they will be allowed to remain in the UK.

While the war crimes that were committed need to be investigated and the Sri Lankan government need to be held accountable for the violence that gripped the country, will an intervention from the international community in denouncing the atrocities really help the Sri Lankan society heal its wounds and move forward? And with a tribunal likely to be set up in The Hague, how will the population on the island feel involved in the judicial processes that will take place?

The problem with the international community is that while it excels at calling for justice and insist on the need for punitive measures to be taken, it lacks proactivity when most needed.

It seems a bit hypocritical to turn around and call for justice once the main atrocities have stopped. The civil war in Sri Lanka lasted more than 25 years and during all this time what did the International community actually do to prevent the killings?