A report by the Australian Crime Commission and Australian Institute of Criminology said high levels of retirement savings made Australians attractive targets.

Home Affairs Minister Jason Clare said men aged over 50 with high levels of financial literacy were the main victims and the losses were likely much higher as people were often too embarrassed to report such fraud.

"The criminal syndicate cold calls the investor, refers them to a flash website and sends them a brochure promising strong investment returns," said Clare.

"After taking their money they string them along for months or even years and then the money disappears.

"These criminal syndicates usually operate from outside Australia. They use front companies and false names. Once they've stolen the money the website disappears and the trail goes dead."

Australian Securities and Investments Commission chairman Greg Medcraft said fraudulent investments were incredibly sophisticated and difficult for even experienced investors to identify.

"Perpetrators of this type of fraud are skilled at using high-pressure sales tactics, over the phone and using email, to persuade their victims to part with their money," he said.

To combat the threat, letters were being sent to every household in Australia warning about the scams.

It is the first time law enforcement agencies have undertaken a mailing campaign on such a scale regarding serious and organised crime.