A decision by Indian Prime Minister Manmohan Singh to skip this week's meeting of Commonwealth leaders in Sri Lanka because of its human rights record has been seized upon by critics.
They say the decision opens the door for China to extend its influence.
Singh is the second leader, after Canadian Prime Minister Stephen Harper, to announce a boycott the meeting, which starts on Thursday.
Their decision is expected to sharpen the focus on the demand by Western nations and rights activists that Sri Lanka account for thousands of civilians suspected to have died in the final months of a quarter-century civil war.
The conflict ended in 2009 when government forces crushed separatist Tamil rebels.
Critics in India slammed Singh's decision as opening the door for rival China, which helps fund Sri Lanka's military and infrastructure projects, to extend its influence. "Now we are vacating our backyard for the Chinese to rebuild all of a booming post-war Sri Lanka," influential columnist and editor Shekhar Gupta wrote in the Indian Express newspaper. "Cancelling now would amount to letting India down without persuading one more Tamil to vote for his coalition."
Singh wrote to Sri Lankan President Mahinda Rajapaksa informing him of his decision not to attend, an Indian government source said.
Singh has been pressed by Indian Tamil groups and several powerful federal ministers to skip the 53-nation meeting to protest at the alleged massacre of Tamil civilians by Sri Lankan forces at the end of the civil war. Singh's letter does not give the reasons for skipping the event, according to the Press Trust of India.
External Affairs Minister Salman Khurshid will instead lead the Indian delegation to the gathering of heads of state of the 53-nation grouping, most of which were formerly under British rule.
"From time to time the prime minister is required to be here and he is unable to visit," Khurshid said yesterday. "It should not be looked at as something that, if such a decision has been taken, will affect India-Sri Lanka relations."
Singh's move has reawakened questions about his legacy after he steps down - as he is expected to do - following next year's elections.
His ruling Congress party has been weakened by a string of corruption scandals, high inflation and stuttering growth after nine years in power.
Singh's landmark foreign policy initiatives, for instance, a 2008 atomic energy deal with the United States that lifted India out of diplomatic isolation over its nuclear programme, have hit major roadblocks.
In a separate development, Sri Lankan authorities yesterday detained and impounded the passports of two lawmakers from Australia and New Zealand who had visited the country's former war zones in the north.
The pair were due to address a news conference organised by the Tamil National Alliance, the former political proxy of the defeated Tamil Tiger rebels.
Authorities say the two were detained because they had travelled on tourist visas. They were later released. Two Australian media activists were held on the same grounds last week.
Sri Lanka was also forced to deny last week that it had refused to give visas to a delegation from an international human rights group, saying permission had not been sought for the visitors.
Additional reporting by Associated Press