THOUSANDS of parents receiving child support from their former partners face lower payments as more lose their jobs.

Welfare groups are concerned the number of parents paying the minimum payment of $12 a fortnight will increase as unemployment rises.

"The human tragedy is that two families could be placed under extra financial stress - not just the family that they are living with, but the family they are assisting through their child support payments," the president of the National Welfare Rights Network, Kate Beaumont, said.

The loss of a job could mean the parent receiving child support gets only $6 a child per week instead of the average of $77 a week. Some of the difference could be made up through increased family tax payments.

Increasing unemployment is likely to make it harder for the Federal Government to ensure parents are receiving adequate money to raise their families.

It is already grappling with a debt in unpaid child support that grew by about 5 per cent to $1 billion last financial year.

This was despite increasingly tough measures used by the Government to recover the money, such as hiring private detectives to spy on people suspected of under-reporting their income and automatically deducting payments from welfare benefits.

The Minister for Human Services, Joe Ludwig, said the Child Support Agency was paying close attention to the effect of rising unemployment on child support payments.

"Many Australians, through no fault of their own, have lost their jobs, had their hours cut back or had their pay reduced as a direct result of the global recession. This can make it especially hard for separated parents to pay child support for the benefit of their children," Senator Ludwig said.

The agency was granted an extra $223 million in last week's budget to offer financial counselling to separated parents whose payments have been affected by changing work circumstances.