NEW DELHI -- Indian Prime Minister Manmohan Singh has decided against attending a Commonwealth summit in Sri Lanka this week over the island nation's human rights record, an Indian official said Sunday.

Singh will be the second leader after Canadian Prime Minister Stephen Harper to boycott the Nov. 15-17 meeting. There are 54 members of the Commonwealth, a loose association of former British colonies.

Their decision is expected to sharpen focus on the demand by Western nations and rights activists that Sri Lanka account for thousands of civilians who are suspected to have died in the final months of a quarter-century civil war that that ended in 2009 when government forces crushed separatist Tamil rebels.

Singh sent a letter to Sri Lankan President Mahinda Rajapaksa expressing his inability to attend the summit, said Syed Akbaruddin, the External Affairs Ministry spokesman. He did not divulge the contents of the letter.

External Affairs Minister Salman Khurshid will represent India at the summit, Akbaruddin said.

India, which has a major interest in the issue because southern India is home to 60 million Tamils, has been urging Sri Lanka's government to resume negotiations with an ethnic Tamil party on increased local autonomy for Tamils.

Singh bowed to pressure from political parties in India's southern Tamil Nadu state, which neighbours Sri Lanka, to boycott the Commonwealth summit on suspicion that Sri Lankan President Mahinda Rajapaksa was not doing enough to protect the interests of the Tamil minority.

After the war, Rajapaksa promised to allow a greater degree of autonomy in Tamil-majority regions in the north. However, he has been criticized by foreign countries and rights groups for failing to deliver on his promises.

Canadian Prime Minister Harper said last month that Canada was disturbed by ongoing reports of intimidation and incarceration of political leaders and journalists, harassment of minorities, reported disappearances and allegations of extrajudicial killings.

Also on Sunday, British Prime Minister David Cameron, who will be attending the summit, said that Rajapaksa has "serious questions" to answer about alleged war crimes committed by his regime in the final months of the civil war.