The ABC board sacked managing director Michelle Guthrie on the same day it launched an independent investigation into claims she made earlier.

The inquiry is being carried out by an external advisor and is continuing, the board said in a statement on Thursday.

The ABC board decided the investigation was needed on September 23, two days after Ms Guthrie’s letter responding to issues raised with her was received.

In the letter, Ms Guthrie flagged other matters she wanted looked at on a confidential basis. The board hasn’t specified what these were.

Ms Guthrie was then sacked on the morning of September 24, with chairman Justin Milne pointing to her relationship with the federal government as a factor.

But Mr Milne was himself forced to quit after it was revealed Ms Guthrie told the board he had requested she sack two journalists because the coalition didn’t like their reporting.

“We are united in defending the independence of the corporation,” the board said in its statement.

“We have done our job thoughtfully and with due regard to board process.”

The directors stressed they had fully debated issues presented to ensure editorial independence was maintained.

Federal Communications Minister Mitch Fifield last week ordered his department to investigate recent issues surrounding the management of the ABC.

David Anderson has stepped in as acting managing director, while existing board member Dr Kristin Ferguson is currently acting chair.

– AAP