Ms Holgate resigned late last year after it was revealed four Australia Post executives were gifted luxury watches for sealing a lucrative deal.

She has attacked Australia Post chairman Lucio Di Bartolomeo in a blistering submission to a Senate inquiry, accusing him of lying to parliament and humiliating her.

The prime minister said he wanted to leave the issue between Ms Holgate and Australia Post.

"Ms Holgate decided to leave Australia Post. That's just a matter of record," Mr Morrison told reporters in Canberra on Wednesday.

An independent investigation later cleared Ms Holgate of any dishonesty, fraud, corruption or intentional misuse of taxpayer funds.

But the accomplished chief executive claims she was bullied out of the company, unlawfully stood down and abandoned to a media firestorm.

"To this date, I have not received any explanation why I was forced to stand down other than the minister and prime minister insisted on it and that in itself, does not have legal standing," Ms Holgate wrote.

Mr Morrison refused to address the perception he threw her under a bus during a stunning Question Time tirade where he called for her to go.

Labor communications spokeswoman Michelle Rowland said the allegations in the 150-page submission were staggering.

"She is clearly very aggrieved by the actions not only by the chair of the Australia Post board but also the prime minister and the minister for communications," she told ABC radio.

Treasurer Josh Frydenberg would not confirm whether the government had sought an explanation from the Australia Post chairman.

Ms Holgate says Mr Di Bartolomeo treated her "like a criminal" and blames him for being forced out of the top job.

"He lied repeatedly to the Australian people and to their parliament about his actions," she wrote.

Ms Holgate's submission also featured emails, photos of handwritten cards and a letter from her lawyers to Mr Di Bartolomeo.

Nationals Senator Bridget McKenzie said she would prosecute significant issues raised in the submission during a public Senate hearing next Tuesday.

Having herself last year resigned after the sports rorts affair, Ms McKenzie suggested some wanted Ms Holgate to return to her post after helping to bring financial stability to regional post offices.

"Her work there was critical to the survival of post offices out in the bush. They feel very strongly about her being reinstated," she told ABC TV on Wednesday.

Australian Associated Press