The communications watchdog has slapped Optus with a near-record $504,000 fine for spamming its own customers.

It’s the second-largest fine ever issued by the Australian Communications and Media Authority, and came after the telco continued to send texts and emails to customers who had unsubscribed from them.

Authority chair Nerida O’Loughlin said on Friday marketers had to respect people’s wishes to unsubscribe.

Optus was also caught sending people fake bills with no options to unsubscribe.

“Australians find spam infuriating and as a regulator it is something we are actively cracking down on,” Ms O’Loughlin said.

“[The fine] reflects the seriousness of breaches made by Optus and its failure to honour its customers’ wishes.”

MEDIA RELEASE: Optus pays $504,000 infringement notice for breaches of spam laws https://t.co/qmEzd0FZmV pic.twitter.com/SkbG4FIofv

— ACMA (@acmadotgov) January 30, 2020

ACMA’s largest fine was levied in 2014 on Telstra, for failing to connect landline customers in time.

Optus will also appoint an independent consultant to make sure it is complying with spam laws.

Ms O’Loughlin said the authority would monitor Optus and might take it to court if it did not comply.

Optus regulatory vice president Andrew Sheridan acknowledged the authority’s actions and apologised to customers “who received the messages in error”.

“We have committed to putting in place enhanced practices and systems to tighten the management of our marketing communications,” he said.

ACMA has raked in more than $1 million in fines in the past 18 months due to the breaking of spam and telemarketing laws.

Corporate offenders caught repeatedly breaking spam laws might face penalties of up to $2.1 million a day, the authority said.

-with AAP