Asylum seekers on Papua New Guinea are self-harming and attempting suicide following the introduction of controversial medical transfer laws because they see it as the fastest way of getting to Australia, the Department of Home Affairs has told federal MPs.

Human rights lawyers swiftly rejected the claims, pointing to the deaths of 12 people in offshore detention before the so-called "medevac" laws were even introduced earlier this year.

The legislation gives doctors in Australia a greater say in whether refugees and asylum seekers should be sent to the mainland for medical care.

The laws were passed against the Coalition's wishes but Prime Minister Scott Morrison has pledged to repeal them following his unexpected victory at the May 18 election.