Britain boycotting the Commonwealth summit in Colombo over alleged war crimes would damage the organisation while achieving no positive change in Sri Lanka, Foreign Secretary William Hague said Sunday.
British Prime Minister David Cameron has said he will be putting "serious questions" to Sri Lankan President Mahinda Rajapakse at the 53-member organisation's biennial summit.
Indian Prime Minister Manmohan Singh will skip the three-day summit, which starts next Friday, while Canadian PM Stephen Harper has urged his counterparts to follow him in boycotting the heads of government meeting.
"We do understand that (boycott), but we're not joining that," Hague told BBC television.
"If we were to stay away from this meeting in Sri Lanka next week, it would damage the Commonwealth without changing things positively in Sri Lanka," he said.
Born out of the British empire, the Commonwealth is made up mainly of former British colonies and brings together around a quarter of the world's countries and a third of its population.
"We need to be there at the Commonwealth meetings," Hague said. "We're discussing there the future of international development, how we're helping developing countries... We can only do that if we're there."
"We are going to say well, Sri Lanka is in the spotlight so let's make full use of it being in the spotlight. Rather than sit in London and talk about it, we will be there in Sri Lanka."
Hague said Cameron would become the first foreign head of government since Sri Lanka's independence from Britain in 1948 to go to the island's mostly Tamil north.
Cameron said earlier Sunday he had watched "No Fire Zone", commissioned by Britain's Channel 4 television, which features footage of apparent war crimes shot by both Tamil witnesses and government soldiers.
"No Fire Zone is one of the most chilling documentaries I've watched," he said.
"It brings home the brutal end to the civil war and the immense suffering of thousands of innocent civilians who kept hoping that they would reach safety, but tragically many did not.
"Many of the images are truly shocking," he said, repeating his call for an independent investigation.
"I will raise my concerns when I see President Rajapakse next week in Colombo.
"And I will tell him that if Sri Lanka doesn't deliver an independent investigation, the world will need to ensure an international investigation is carried out instead."