Opposition Leader Tony Abbott has set a Coalition government the target of limiting unauthorised boat arrivals to three a year, saying he deserves to be "very harshly judged" if it fails.

Mr Abbott said on average three boats a year had arrived under previous Coalition governments between 2002 and 2007, and he was aiming for the same result.

"If I can achieve three boats a year ... I think the Australian public would have every reason to be grateful to the new government," he told reporters in Sydney today.

Mr Abbott said he would regard as having "very substantially succeeded" if arrivals could be kept to three a year, adding he hoped to make a significant difference to boat arrivals within three months of being elected.