LONDON (Reuters) - Leading British lawmakers urged the European Union on Thursday to remove preferential trade tariffs from Sri Lanka if it fails to address human rights concerns.

Sri Lanka has refused to cooperate with a United Nations Human Rights Council investigation into war crimes allegedly committed by both state forces and separatist Tamil rebels during a conflict that ended in 2009, despite mounting international pressure.

The United Nations has estimated about 40,000 civilians were killed in the final weeks of the 26-year conflict, mostly by the army, but Sri Lankan President Mahinda Rajapaksa has dismissed the probe as politically motivated.

The EU is Sri Lanka’s largest export destination, accacounting for 36 percent of Sri Lanka’s total exports, according to EU figures.

“Our government must negotiate with EU partners to remove trade concessions from Sri Lanka if the government of Sri Lanka continues to deny the U.N. investigating team access into the country,” Richard Ottaway, a Conservative lawmaker and chairman of parliament’s foreign affairs committee, said in a statement accompanying a report on the government’s work on human rights.

While the EU has temporarily withdrawn some trade concessions, Sri Lanka remains a beneficiary of the Generalised Scheme of Preferences, which allows developing country exporters to pay less or no duties on their exports to the EU.

During a summit of Commonwealth nations in Colombo a year ago, British Prime Minister David Cameron was a vocal critic of Sri Lanka’s human rights record, and Britain was among those who pushed for the international inquiry.

“The government should be ready to consider all possible options, including sanctions, to convince Sri Lanka to allow access,” the British lawmakers said in the report.

The lawmakers said the government should use the opportunity of a new administration in Sri Lanka’s neighbor India to garner regional support for the investigation. India abstained from a vote to back the inquiry at the United Nations in March.