Physicians are concerned proposed plans to drug test welfare recipients will have considerable consequences for those battling addiction.

Plans to drug test Australians on welfare won't work and could seriously harm those battling addiction, says The Royal Australasian College of Physicians.

The RACP - which represents more than 15,000 physicians across Australia and New Zealand - will on Friday lodge its its submission to an inquiry into the federal Social Services Legislation Amendment (Welfare Reform) Bill 2017.

Legislative changes being proposed will force about 5000 Newstart and Youth Allowance recipients to undergo drug testing and subject them to a variety of restrictions if they test positive.

The RACP is "strongly" opposed and is urging the federal government to instead "appropriately" invest in alcohol and drug treatment services.

"RACP members see first-hand the many and varied harms caused by addiction when treating their patients in Australia's addiction clinics, rehabilitation centres, liver clinics, cancer wards and hospital emergency departments," the submission states.

Drug and alcohol addiction is a serious, complex health problem and there is "absolutely" no evidence to show drug testing trials will work, says RACP President Dr Catherine Yelland.

The experience of countries like America and New Zealand, she says, have shown drug testing has a poor record in modifying drug use.

"Similar programs have been shown to be ineffective in identifying people with substance dependency and have been criticised for discriminating against some of the most vulnerable people in those communities."

The RACP also has serious concerns about amendments that will remove drug and alcohol dependency as a legitimate reason for jobseekers to not meet participation requirements.

It won't help addicts and it won't motivate them to seek treatment, Dr Yelland says.

"Taking payments away from these people will only cause even greater hardship and a likely spiral into worse health," she said.