The federal government is urging Bill Shorten to condemn union robocalls it says represent a new low in Australian politics, designed to "scare the hell" out of pensioners.
But the opposition leader is adamant the government should look at its "disturbing" policies before shooting the messenger.
The ACTU is behind the anonymous automated phone calls, purported to be from a woman named Leanne, warning of changes to the pension from January 1.
"I'm worried about my dad," she says.
"He's just had a letter from the government saying Malcolm Turnbull will be cutting his pension.
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"Him and mum worked hard their whole lives so how can the government suddenly make changes now, and just before Christmas?"
Leanne then urges her listener to call talkback radio and the prime minister's office to complain about the "un-Australian" changes.
Social Services Minister Christian Porter says the calls are deliberately designed to deceive and scare people about changes that were taken to the July 2 election and ultimately supported by Labor and the Greens.
If Mr Shorten doesn't condemn them, he's a party to them, he said
"Every time you think there's a new low in Australian politics reached, the union movement manages to go just that little bit lower," he told 2GB on Thursday.
"What this call does is go out completely indiscriminately to families in electorates and it is specifically designed to scare the hell out of pensioners unnecessarily, dishonestly and quite shamefully.
"It is one of the lowest acts I can recall hearing about or seeing in Australian politics."
Mr Shorten said the government was leaving pensioners worse off to give tax cuts to big companies and millionaires.
"All we see here is the Turnbull government shooting the messenger but not having a look at why people are unhappy," he told reporters in Melbourne.
The government insists the changes will leave 90 per cent of pensioners unaffected or better off.
The remaining 10 per cent who have high assets on top of their family home will lose the pension, or part of it.
It's expected 88,000 people will lose the pension as a result of the changes and 225,000 will have a reduction.
Human Services Minister Alan Tudge says pensioners most likely to be hit were informed by letter in October and more recently notified about the exact changes to their pension.
All pensioners will continue receiving the seniors healthcare card but Mr Tudge said it was up to state and territory governments to determine whether they'd still be entitled to pensioner concession cards for discounts on bills and public transport.
"We've got an ageing population, we've got a smaller proportion of people who are working to support that ageing population and indeed the forecasts are that in 40 years' time we'll have twice as many pensioners as we do today," he told ABC radio.
"So we have to make sure that that system is sustainable."
