Cameron said he pressed President Mahendra Rajapaske during this year's Commonwealth heads of government meeting in Australia to show that Colombo did not "have things to hide" following the end of the country's civil war.
Sri Lanka's foreign minister has revealed that he had stopped Canada from raising during the talks a UN-commissioned report which alleges that the military massacred civilians in 2009 in the final stages of the Tamil rebellion.
Put to him in a BBC interview from Perth that Canada might boycott the 2013 meeting, Cameron said: "I've been discussing this with the Canadians and I think we all have a similar view, which is we want to see Sri Lanka do more in terms of human rights, we want them to do more in terms of reconciliation after the defeat of the Tamil Tigers.
"I've had that conversation myself with President Rajapakse, who's here.
"They should be aware of the fact that they're holding this Commonwealth summit in 2013 and it's up to them to show further progress s