Claims of stolen same-sex marriage ballots, weather-damaged postal survey envelopes and other anomalies have prompted a stern warning from the Australian Bureau of Statistics and calls for the entire process to be scrapped.

The survey has been marred by anecdotal complaints since the ABS began mailing out ballot papers, including that some had been sent to residents’ former addresses, sparking concerns that they could be filled out illegally.

At the weekend, survey envelopes at seven Canberra apartment blocks were reportedly found left out in the rain rather than delivered to individual letter boxes, while a Senate committee on Friday heard claims that some people had received postal packs without reply paid envelopes.

The committee also heard complaints from a person who reported “what might have been stolen envelopes ripped open and left on the ground” in Melbourne.

Growing concern over the survey prompted a response on Monday from the ABS, which said the process was on track and proceeding to schedule.

Deputy Australian statistician Jonathan Palmer conceded the ABS was aware of reports that people had opened former tenants’ mail and completed their survey forms.

“If you receive a survey form not addressed to you, do the right thing and just return it to sender. It’s illegal to open others’ mail, unless you have their express permission as a trusted person,” he said.

“Stealing or tampering with mail is a criminal offence that carries serious penalties.”

Complaints pile up

Since ballots were mailed out, a number of social media users have boasted of filling out the postal surveys of former occupants of their homes.

In the New South Wales town of Orange, a woman found multiple postal survey forms dumped in her recycling bin with the voting forms missing and identification ripped off the letter.

The ABS has also asked the Australian Federal Police to investigate instances of postal surveys being sold on eBay, with one seller advertising theirs for up for $1500.

The bureau told a Senate committee on Friday it had asked for online marketplaces to remove up to 20 ads so far.

The committee heard that the ABS had received 87,000 phone calls to a an information hotline, of which four per cent were complaints and 1 per cent have been compliments.

There have also been privacy concerns after social media users revealed that a person’s vote could be seen through an envelope using a torch.

One Nation leader Pauline Hanson, who does not support same-sex marriage, argued that the $122 million survey should be scrapped.

“I think it is a waste of millions of dollars. Then again, if it comes through, whether it is Yes or No, is the Parliament going to uphold it?” she said.

“I think it is farcical. I think it is a joke. It should have gone to the next election.”

‘Credibility undermined’

Monash University political expert Nick Economou said there was a real risk of fraud because a person in one household could easily fill out and send back multiple ballots.

“It’s one of the most insecure ballots I’ve ever seen,” Dr Economou told The New Daily.

Asked if reports of stolen ballots and other anomalies could undermine the credibility of the result, Dr Economou said: “The credibility was undermined from the start.

“From the moment the Parliament refused to accept it as a plebiscite and the process was going to be run by the ABS rather than the electoral commission.

“The critique of postal voting has always been that these problems could always arise.”

An Australia Post spokeswoman said: “Our posties are delivering all survey items securely and as addressed, as they do with all mail items.”

On the specific concerns around ballots in Canberra at the weekend, the spokeswoman said: “We are confident that all survey items are being delivered securely and as addressed, as they do with all mail items.”

“Australia Post has robust security measures in place throughout our national network and have added additional measures in place for the duration of the survey delivery process.”

“We urge customers to be vigilant to ensure their mail is secure, and If anyone suspects mail tampering or theft has taken place, we recommend they contact local police immediately.”

Ballot papers are due back on October 27 with the result to be announced on November 15.