Changes announced in the May budget mean about 150,000 parents will no longer be paid the sole parent payment but will instead receive the dole when their youngest child turns eight, a drop in income of between $60 and $110 a week.

Welfare groups say people affected by the changes believe their payments will be automatically adjusted instead of having to reapply for the dole, or Newstart Allowance.

''It is deeply disturbing to find that single-parent families may be left without any income when the new rules start on January 1 next year,'' the president of the National Welfare Rights Network, Maree O'Halloran, said.

''Those parents who have not heard the bad news will not have made a new claim for the Newstart Allowance.''

The change, which angered many Labor MPs, is budgeted to save the government more than $700 million over the next four years.

Ms O'Halloran said it was ''unacceptable'' that families could be left without any government payments because they did not know they would have to complete additional paperwork.

''The legislation does not help parents find more hours of paid work and these are the families that can least afford cuts,'' Ms O'Halloran said.

Minister for Human Services Kim Carr said 300 Centrelink staff had been trained to make sure people affected by the changes were contacted in advance of the January 1 changeover.

''For many people, everything will be explained and organised for them in just one phone call,'' Senator Carr said.

The department is meeting welfare and church groups as part of its attempts to reach people affected by the changes.

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