Sacked ABC managing director Michelle Guthrie has won an improved secret pay day from taxpayers to leave the national broadcaster, with her final payout now estimated at more than $1.3 million.

Ms Guthrie’s original termination settlement was bumped up by an additional $500,000 on Friday – according to reports on Monday – in a final attempt to convince her to drop an unfair dismissal case before the appointment of new chair, Ita Buttrose.

While some ABC sources claimed last night that figure was “not correct”, hinting it could be even higher, the true figure could be revealed on Tuesday during “in camera” hearings of a Senate committee.

The ABC remains deeply concerned that if the confidential settlement is leaked, the matter could return to the courts.

The Australian Financial Review reported that a last-minute legal hitch delayed completion of the deal until after Ms Buttrose’s press conference with Prime Minister Scott Morrison on Thursday.

Ms Guthrie had previously asked to be reinstated in the job, a standard tactic when attempting to negotiate a larger termination payout.

A spokesman for Ms Guthrie told The New Daily he had “no comment” on the payout figure. It’s understood a confidentiality clause and a non-disparagement clause stopping ABC directors from launching further attacks on Ms Guthrie’s leadership are part of the deal.

The unfair dismissal battle had quickly degenerated into sensational claims the former ABC chairman Justin Milne had acted inappropriately towards Ms Guthrie – claims he strenuously denied.

Mr Milne had also accused Ms Guthrie of fabricating conversations where she insists he urged her to sack journalists Emma Alberici and Andrew Probyn.

However, the saga is likely to come under further scrutiny at a Senate inquiry into political interference.

The ABC will hold hearings on Tuesday, where the national broadcaster’s acting managing director David Anderson is expected to appear.

Communications Minister Mitch Fifield has already rebuked the ABC for attempting to keep Ms Guthrie’s payout secret after news of the confidential deal was made public.

“Neither the government nor the community are aware of the terms of the settlement due to the legal agreement,” a spokesman for the minister said.

“The government’s preference would be for the parties concerned to be transparent in relation to any part of the settlement that may involve payment and receipt of taxpayer funds.”

Ms Guthrie was already paid $800,000 to leave the job when she was sacked in September. She was fired halfway through her five-year contract.

Her annual salary was $900,000.