The federal government has little chance of finding out if the first three years of its controversial $18 million cashless welfare card trial have been a success because the department running it failed to deliver a cost-benefit analysis and gave misleading statistics to the minister in charge.

The findings of a $483,000 audit by the Australian National Audit Office released on Tuesday have been accepted by the Department of Social Services and are likely to be latched onto Labor to ramp up concerns about the card as it campaigns in the relatively high-welfare electorates of Longman and Braddon.

The card prevents 80 per cent of all disability, parenting, carers, unemployed and youth allowance payments from being withdrawn as cash or used to gamble, buy drugs or alcohol.

Since 2014 the card has been trialled in Ceduna in South Australia and Western Australia's East Kimberley, while WA's Goldfields region was added to the program last year.

The report delivered by Auditor-General Grant Hehir praised the card's implementation process but found evidence of better health and welfare outcomes had been compromised by multiple statistical failures by the department.