More than 5000 doctors have signed a petition calling on senators to preserve a law that makes it easier to bring refugees in offshore detention to Australia for medical treatment.

The Morrison government is hoping to repeal the law, passed against its wishes in February, but the doctors are urging independent senator Jacqui Lambie to use her casting vote to keep it in place.

Professor David Isaacs of the Royal Australasian College of Physicians said that with people dying on Manus Island and Nauru, it is imperative that doctors are the ones who decide who comes to Australia for urgent medical care, rather than politicians.