The mid-year economic forecast tables published last week shows the government has booked savings of $1.1 billion clawing back overpayments of the aged pension and another $400 million from the disability support pension.

The tables also show the government believes it can retrieve another $700 million from hundreds of thousands of Australian families who receive parenting payment or have been paid the benefit in the past.

The moves could bring up to four million more Australians into the sights of the data-matching program, which uses an automated system to match information held by Centrelink and the Australian Taxation Office and calculate overpayments.

Centrelink's parent department, Human Services, confirmed on Tuesday that its data matching technology would be picking up any income from investments, business or real estate declared to the ATO, usually in annual tax returns going back many years, but not to Centrelink.

A departmental spokesman said the activity, which could lead to debt collectors being called in or even criminal prosecution, was "normal".

But the policy has been beset by errors and has been hugely controversial with many of those targeted for debt recovery saying they are being hounded by debt collectors, or threatened with jail, for money that they do not owe.

Elderly Australians have already begun contacting Fairfax to say they have been received letters generated by the data matching program.

Have you been hit with an age pension robo-debt? Contact us ps@canberratimes.com.au

After weeks of concerted protest against the robo-debt campaign, Human Services Minister Alan Tudge Tudge agreed this week to make some modifications to the letters, which he insists are not debt letters, but pledged to push ahead with the campaign which the government says will add $4.5 billion overall to the budget bottom line

But he has not satisfied the program's many critics who want it shut down until the high rate of bogus debts being generated can be addressed.

The data matching effort so far has been concentrated overwhelmingly on mostly young people who have received the dole or Youth Allowance, although evidence is emerging that students have also been hit heavily.

But the supporting tables to the government's mid-year financial and fiscal outlook, published on Thursday by the Parliamentary Budget office, reveal that Coalition policy is to massively extend the data matching effort to the more than 2.5 million age pensioners and about 800,000 disability support pensioners.

The papers also reveal that the government believes it will slash spending by $400 million on the disability support pension and $700 million on parenting payment.

Centrelink spokesman Hank Jongen said that people caught in the data dragnet would first be asked to clarify their position.

"It is important to note that these measures only pick up those cases where the information declared to the ATO is different to that declared to Centrelink," Mr Jongen said

"In the first instance people are simply asked to either update or confirm their details.

"The Mid-Year Economic and Fiscal Outlook measures are intended to extend the current compliance activity for non-employment income, assets and investments e.g. income from financial investments, business and real estate that has been declared to the ATO."