Opposition immigration spokesman Scott Morrison and deputy opposition leader Julie Bishop said a Coalition government would use the Australian navy to turn back asylum seeker boats.
The Australian Navy would be charged with repelling Sri Lankan asylum seeker boats outside Australia's international borders under a Coalition government.
Shadow immigration spokesman Scott Morrison said a Coalition government would turn all Sri Lankan boats around, without exception.
Mr Morrison and deputy Liberal leader Julie Bishop were speaking about their recent trip to Sri Lanka, which they said showed the country was returning to safety after the civil war.
He said the pair had been told the greatest threat to Sri Lankans' lives was getting on a boat rather than staying in the country, and the primary motivation for those coming to Australia was ''economic and lifestyle''.
Their comments come in the wake of a UNHCR report slamming conditions
for asylum seekers on Papua New Guinea's Manus Island and urging the new Immigration Minister, Brendan O'Connor, to stop sending people to the centre until the report's recommendations are implemented.
In a further sign of the tough policies the Coalition will campaign on before the September election, Mr Morrison flagged that Australian forces would be involved in forcibly repelling asylum seeker boats from reaching Australian waters, where they would engage Australia's international refugee protection commitments.
He claimed this would not put Australia in breach of its international laws, because the Refugee Convention does not have extra-territorial powers, and the returns would be done in international waters. But the convention forbids Australia from returning people to countries where their life or freedom would be threatened on account of his race, religion, nationality, membership of a particular social group or political opinion.
Mr Morrison stopped short of saying how he would achieve the forced returns in international waters, saying he did not wish to give a ''heads up'' to refugee lawyer David Manne. Mr Manne led the successful High Court challenge to the Malaysian solution, among other high-profile cases.
He insisted, however, that the policy was safe and could be done compassionately.
Australia would be unable to forcibly remove asylum boats once they reached Australian waters without first giving asylum seekers the chance to make their case for Australia's protection under refugee laws.
The Greens' immigration spokeswoman, Senator Sarah Hanson-Young, said the returns would be in clear breach of international laws.
''It simply can't be done. It can't be done legally,'' she said.
''The Coalition and Tony Abbott are prepared to do anything including illegal acts in order to continue their get tough, get cruel, get mean race to the bottom on refugees.''
Greens leader Christine Milne said conditions were still not safe for Tamils in Sri Lanka.
''People are disappearing in white vans, never to be heard of again,'' she said.
Mr Morrison said that even for people who felt they had a case for asylum, the safer option was to stay put rather than get on a boat for Australia. For this reason, he said: ''Our policy of ensuring that all boats who would seek to come to Australia illegally would be returned.
''They will be intercepted outside our sea border and it will be arranged for them to be returned to Sri Lanka.''
Asked to clarify whether that meant the Australian Navy would be sent to intercept boats outside Australia's borders, Mr Morrison said: ''That is our policy.''