Mr Marles said he had asked the ADF to "urgently investigate" the claims, saying a deep evaluation of defence policies and procedures was warranted.
"The information provided to me so far presents enough evidence to warrant the need for a detailed examination into the adequacy of current defence policies and procedures addressing this matter," he said on Wednesday.
"I have therefore instructed the department to commence that process."
A number of cases of foreign interference are being investigated by the Australian Federal Police and Australian Security Intelligence Organisation along with the ADF.
"It's no secret that defence activities, people and assets are targets for Foreign Intelligence Services," Mr Marles said during a press conference at Parliament House.
"But let me be clear, Australians who work or have worked for the government in any capacity, particularly our ADF, who come into possession of the nation's secrets, have an obligation to maintain those secrets beyond their employment with, or their engagement with, the Commonwealth."
Mr Marles wouldn't confirm if a specific incident had kicked off the investigations into the alleged foreign interference cases.
But policies and procedures relating to former defence force personnel should be reviewed to ensure they are adequate, he added.
