The government's victory over the Tigers ended a bloody civil war
Sri Lankan President Mahinda Rajapaksa has denounced plans by UN chief Ban Ki-Moon to ask a panel of experts to look into human rights issues on the island.
Mr Rajapaksa told Mr Ban the move was "uncalled for and unwarranted", the president's office said in a statement.
Human rights groups want some sort of accountability for abuses alleged to have been committed during the war against Tamil Tiger separatists.
The Sri Lankan government insists it did nothing wrong.
Mr Ban plans to ask a panel of experts to advise the UN on "accountability issues" relating to possible human rights abuses in Sri Lanka, his spokesman said on Friday.
But Rajapaksa's office said the president spoke to Mr Ban by telephone on Friday and told him that alleged rights abuses were "misrepresentations" by supporters of the Tamil Tigers and other groups working against Sri Lanka.
"President Rajapaksa has pointed out that the intention of the UN Secretary General Ban Ki-moon to appoint a panel of experts to advise him on Sri Lanka is totally uncalled for and unwarranted," the statement said.
It said the panel would "certainly be perceived as an interference with the current general election campaign", referring to next month's poll.
The statement added that Sri Lanka would take "necessary and appropriate action", but did not specify what that would be.
Mahinda Rajapaksa aims to win a majority in parliament
The BBC's Charles Haviland in Colombo says that three decades of ethnic war were disastrous for human rights in Sri Lanka but the current government - like others before it - is very sensitive when the issue is raised.
A joint UN-Sri Lankan statement last May said the government would take measures to address grievances concerning possible war crimes. But the government's critics say it has not followed through on this.
The UN has reported that more than 7,000 civilians died as government forces closed in and crushed the rebellion in the north of the island last year.
The government has been accused - among other things - of firing heavy weapons into civilian areas, and the Tamil rebels have been accused of holding civilians as human shields.
Mr Rajapaksa, who won a second term as president in January, has called parliamentary elections for 8 April hoping to further tighten his grip on power by securing a majority in the 225-member legislature.
In another development, Indian Foreign Secretary Nirupama Rao arrived in Sri Lanka for talks, meeting Mr Rajapaksa in Colombo.
In a statement released by Colombo, a spokesman for Mr Rajapaksa said the pair discussed the issues of Sri Lankan Tamils uprooted by civil conflict in 2009.
According to the statement, Ms Rao noted that Sri Lanka had had "considerable success" in resettling some of the 70,000 people forced to leave their homes during Colombo's offensive against the Tamil Tigers.