Sasako says Sogavare told him - and others - that he'd had a lengthy meeting in his office with the deceased Mamaloni.
Political leadership was discussed and Australia was singled out as a country not be trusted before Mamaloni got up and left the room,Sasako says in an article written for the July edition of Islands Business magazine.
"It was then that I realised I had been talking to a dead man,"Sogavare reportedly told Sasako.
Sogavare also confided in others that his meeting with Mamaloni inspired him to seek the prime minister's job a second time round,Sasako said.
The former MP has also accused Sogavare of listening to fortune tellers,including one who warned him about assassination attempts.
Sasako claims Sogavare's belief in the prediction led to the arrest of an Australian Vietnam War veteran,who was later charged with plotting to kill the prime minister.
Sasako said he was told by a former secretary to Sogavare how she was invited into his office where he said:"A fortune teller told me that I would be assassinated by a white man".
Three weeks later,on January 30 this year,61-year-old Australian Vietnam war veteran and longtime Solomons resident Bill Johnson was arrested and charged with plotting to assassinate the prime minister.
Solomons residents who knew Johnson reacted in disbelief to the charges.
They were later withdrawn by the Director of Public Prosecutions after he found police witnesses had changed their statements and the accusations could not be substantiated.
Sasako said that a week after Johnson was freed,the secretary was again called to Sogavare's office to be told the threat of an assassination was not over.
This time it would be carried out"by a light-skinned woman close to me and working in this office".
The secretary said the prime minister asked her:"I want to know,would you do it?"
The secretary left Sogavare's office and shortly afterwards left the job.
The magazine article prompted Opposition Leader Fred Fono this week to accuse Sogavare of being a hypocrite in seeking the support of the churches when he also trusted fortune tellers.
Sogavare,a devout Seventh Day Adventist,strongly denied the claim,the Solomon Star newspaper said.
Since his election in May last year,Sogavare has been embroiled in a series of disputes with Canberra and the Australian-led Regional Assistance Mission to Solomon Islands (RAMSI).