One of the few Indigenous community leaders who backed the cashless welfare card in its infancy has changed her mind, accusing the government of running a "brutal" program that has become little more than a "big stick to punish the poor".

Professor Marcia Langton told the National Press Club that a botched government roll out had changed her mind on the cashless welfare card, which quarantines 80 per cent of unemployment and various other welfare payments to prevent them being spent on alcohol, drugs or gambling.

Marcia Langton says the cashless welfare card roll out has been "brutal". Credit:Arsineh Houspian

The government hopes to put 22,500 people in the Northern Territory and Cape York on a similar trial program that quarantines 50 per cent of users' funds.

"It is a tragedy that the Department of Social Services, the Department of Human Services and others responsible have not implemented the scheme in accordance with the original design and in accordance with the commitments they made to those community people, to those elders, to those leaders," the Australian Indigenous Studies chair said on Wednesday.