India's prime minister is boycotting a Commonwealth summit in Sri Lanka next week over the island nation's human rights record, an official said today.

Manmohan Singh will be the second leader after Canadian prime minister Stephen Harper to snub the November 15-17 meeting of the 54 member Commonwealth, an association of former British colonies.

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

New Delhi will announce Mr Singh's decision by tomorrow, the official 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.

Mr Singh bowed to pressure from political parties in India's southern Tamil Nadu state neighbouring 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, Mr Rajapaksa promised to allow a greater degree of autonomy in Tamil-majority regions in the north. However, he has been criticised by foreign countries and rights groups for failing to deliver on his promises.

Mr 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.