A former banker who is suffering repeated online attacks on his character and integrity after becoming a witness for the Australian Securities and Investments Commission (ASIC) has warned other people to "run like they're on fire" if asked to provide evidence on financial scammers.

Key points: Mortgage broker Graeme Holm urges people to "run" to avoid being a witness for ASIC

Mortgage broker Graeme Holm urges people to "run" to avoid being a witness for ASIC He says an online smear campaign has plunged his business into costly damage control

He says an online smear campaign has plunged his business into costly damage control His case has prompted further calls for a whistleblower protection authority

Graeme Holm said damaging online harassment of him and his finance business began just hours after the corporate watchdog announced a ban on a mortgage broker based on his testimony.

ASIC, which pursued the broker as part of its investigation of a $65 million property spruiking racket, has said it "regrets the harassment and defamation" he has faced but it cannot help.

The case has prompted further calls for a national whistleblower protection authority.

"I guess you would say ASIC have what they need, they got their prosecution and their evidence and good luck to me. I just have to deal with it and so do my staff and my clients," Mr Holm told the ABC.

"I would say to anyone that ASIC reaches out to run — and run like you're on fire.

"Don't return their calls. Do not engage. They will not support you.

"You may think you're doing the right thing but it will hurt you in the long run and they won't protect you."

Mr Holm said his lawyer had told him not to turn witness against the mortgage broker after ASIC first called him in late 2016.

He had worked at Westpac when the broker submitted loan applications to the bank containing information ASIC found to be false.

"ASIC did advise that they had the powers to compel me to [give evidence] and throughout the process, going backwards and forwards with ASIC, eventually it felt like the right thing to do and to be a good corporate citizen," he said.

"I was one of the only professional services people that provided testimony to ASIC, so I believe it may have been fairly crucial."

Graeme Holm's award-winning finance business has been under seige online since he became a witness for ASIC. ( Supplied: Graeme Holm )

Mr Holm said the "online smear campaign", which began in February, had plunged his Infinity Group business into costly damage control and had scared off customers.

He said the attacks had escalated to include "disgusting, inflammatory, false, vulgar videos, photos, false complaints, you name it".

"The impact on my family, my clients and my friends, I don't wish it upon my worst enemy," he said.

"We've lost an abundance of potential clients who have been in the midst of doing business with us who have terminated the relationship because of what's online.

"We've had examples where clients have felt obliged to go to ASIC and complain about us just because of what they read on the internet."

Graeme Holm was hailed as one of the nation's top mortgage brokers by his Australian peers. ( Supplied: Graeme Holm )

Most of the attacks are on US-based websites that routinely ignore defamation orders by Australian courts, such as Ripoff Report.

Mr Holm said some were on websites where "you have to pay an exorbitant amount of money for them to investigate the comments".

He said his business, which has won awards including being named one of the country's most innovative companies by the Australian Financial Review, was "unable to locate a single client" whose details match complaints on the internet.

In the wake of the attacks he appealed to ASIC, which can compel witnesses and make referrals to state and federal police.

But a lawyer in ASIC's financial services enforcement division last month emailed him to say they would not be helping.

"ASIC has considered the material you provided and regrets the harassment and defamation [Mr Holm] has been subject to," the ASIC lawyer said.

"However, as advised, unfortunately ASIC is not in a position to assist [him] with this matter."

Mr Holm told the ABC he was "disgusted" by the response, given ASIC's regulatory and investigative powers and links to law enforcement.

"They're meant to protect the community, they're meant to protect people that they've engaged to come forward and state the facts," he said.

"They have the power to stop things like this from happening yet they choose not to."

Griffith University professor AJ Brown, who is leading a push for greater whistleblower protections, said it was crucial to resolve cases like this to show people they "won't suffer an injustice for speaking up about wrongdoing".

Professor AJ Brown is leading a push for stronger whistleblower protection. ( ABC News )

"Every regulator who's involved in taking witness evidence needs to be looking at those witnesses … but I think it does emphasize there's only so much they can do to protect them very often," he said.

"That's why there really does need to be stronger law reform and specialist institutions to help look after exactly that challenge."

The Morrison Government has flagged introducing new amendments to whistleblower protections in the Corporations Act later this month.

Last week, independent MP Cathy McGowan confirmed her plan for a new federal corruption watchdog would include a whistleblower protection authority.

Professor Brown said an agency dedicated to protecting whistleblowers would help regulators that "themselves might not be able to do it every time".

"What we need to do is actually to make that easier, so that the protection is there right from the word go and it's clearer that if you do suffer repercussions, there will be justice for that."

Attacks 'absolutely' retaliation for ASIC cooperation

An ASIC spokesman did not directly address questions about Mr Holm's case or steps taken by the agency to protect witnesses.

He referred the ABC to a 12-page information sheet outlining "how we manage the many competing priorities" in enforcement.

On its website, ASIC states that it "can and does" investigate claims of victimisation against whistleblowers.

But it also stipulates this is not its main focus, because of "limited resources", and urges individuals to privately pursue their rights to protection under the Corporations Act.

Mr Holm said the timing of the online attacks meant there was "absolutely no doubt in my mind" they were retaliation against his evidence to ASIC.

"We've been trading since 2013 and until this year there was not a bad word said on the internet about us," he said.