By Peter Griffiths
LONDON (Reuters) - British Prime Minister David Cameron said on Thursday he will demand that Sri Lanka investigates allegations of war crimes and human rights abuses when he visits the country for a meeting of Commonwealth leaders next week.
Cameron said he wanted to "shine the international spotlight on the lack of progress" in the Indian Ocean island since the end of a long civil war in 2009.
Defending his decision to attend the biennial Commonwealth leaders' meeting in the capital, Colombo, Cameron said he would have a better chance of securing changes if he pressed ahead with his visit to the former British colony.
"I will demand that the Sri Lankan government independently and transparently investigates alleged war crimes and allegations of continuing human rights abuses," Cameron wrote in an article for a London-based Tamil newspaper.
Human rights groups have urged leaders to boycott the November 15-17 meeting to put pressure on the Sri Lankan President Mahinda Rajapaksa.
Canadian Prime Minister Stephen Harper has said he will not attend, citing concerns over allegations of extra-judicial killings, harassment of minorities and the detention of politicians and journalists.
South African peace campaigner Archbishop Desmond Tutu said he supported a boycott, urging the world to "apply all the screws that it can".
The Sri Lankan government says its rights record has improved since the war and has rejected the criticism as unsubstantiated.
Tens of thousands of civilians died in the last months of the war between the government and the Liberation Tigers of Tamil Eelam (LTTE) rebels, who lost their fight for a separate state for Sri Lanka's Tamil minority, a U.N. report estimated.
Cameron said he would become the first foreign leader to visit the north of the island since the country's independence from Britain in 1948. The war ended in 2009 when government forces surrounded the rebels in a small area in the north.
"Four years after the conflict, no one has been held to account for grave allegations of war crimes and sexual violence, journalists are routinely intimidated and thousands of people have yet to find out what has happened to their missing relatives," Cameron wrote.
Britain's opposition Labour said Cameron had failed to exploit his visit to push for improved human rights.
"The British government's handling of this issue has been characterized by misjudgments and missed opportunities," Labour foreign affairs spokesman Kerry McCarthy said.
(Editing by Ralph Boulton)