Linda Burney, Labor's human services spokeswoman, has written to the Australian National Audit Office requesting they investigate Centrelink's controversial $4.5 billion debt clawback project amid ongoing accusations that it is unfairly targeting people and miscalculating bills.

The opposition and community groups are maintaining pressure on the government as the new system, enabled by data-matching with Australian Taxation Office information, causes consternation by handing out mistakenly oversized debts and contacting some social security recipients who don't owe Centrelink any money.

Ms Burney's letter to Auditor-General Grant Hehir requests that, in light of "overwhelming" constituent complaints about the contentious process, the ANAO examine the effectiveness, risk management and planning of the system and the actual value of the resulting budget savings, including analysis of whether falsely calculated debts have already been banked.

"There is considerable public concern over the administration of this program as well as a lack of clarity around the value of 'savings' derived from the program to date," she said in the letter, provided to Fairfax Media.