Australia is to donate two navy patrol boats to Sri Lanka as part of a joint effort aimed at combatting people smuggling.

Prime Minister Tony Abbott, who is in Sri Lanka for the Commonwealth Heads of Government Meeting, agreed to the deal with president Mahindra Rajapakse this weekend.

The deal has been criticised by the Greens, but Labor has offered some support for closer ties with the island nation.

Meanwhile a top Sri Lankan minister has rejected pressure for an international probe into alleged war crimes at the end of Sri Lanka’s ethnic conflict, saying the government would “definitely” not allow one.

“Why should we have an internal inquiry? We will object to it … Definitely, we are not going to allow it,” Economic Development Minister Basil Rajapaksa, who is President Mahinda Rajapaksa’s brother, told AFP on Saturday.

His comments came after British Prime Minister David Cameron said he would push for an international investigation through the UN human rights council unless the government acted by March to credibly address claims of abuses.

The Rajapaksa regime is enacting its own more limited investigation but denies civilians were killed in the final stages of the war, when government troops routed Tamil Tiger rebels in their last stronghold.

The UN and rights groups say as many as 40,000 civilians may have been killed in the onslaught.

“It is not new, it is not the first time they are saying it,” Basil Rajapaksa said of the pressure for an international inquiry.

Asked about the March deadline for the Sri Lankans to complete their inquiry, the minister rejected talk of a timetable being imposed from outside.

“They can’t give dates. It is not fair. Even Cameron has said we need time. Even in Northern Ireland it took a lot of time,” he said.

Cameron infuriated the government in Colombo by travelling to the war-torn northern Jaffna region on Friday to meet Tamils, hours after a Commonwealth summit began in the capital.

The prime minister said he was moved by the “harrowing” testimony of survivors.

“We understand some of the things he said were aimed at his home constituency,” the minister said, thanking Cameron for attending the summit.

The prime ministers of Canada, India and Mauritius stayed away from Colombo over Sri Lanka’s human rights record.