The ABC has already interviewed for a replacement news boss and will “imminently” move to name a successor for Justin Stevens after his surprise departure.

Managing director Hugh Marks addressed Senate estimates on Thursday, a day after Stevens announced his departure from the key post after four years for “reasons both professional and personal”.

Liberal senator Sarah Henderson, the Coalition’s communications spokeswoman, said it “very much looks like he (Stevens) was pushed … and was on the chopping block” for recent controversies.

While not commenting on Stevens’ situation, Marks said the decision meant the ABC could renew.

“It’s an opportunity, obviously, for the ABC to enter into a new phase of operations, where we look to, you know, refresh and rejuvenate our output … to make sure that we’re future fit,” he said.

Stevens, who was executive producer of 7.30 before taking over as news chief, had nearly two decades at the ABC.

His resignation, which took immediate effect, was announced in an email to the broadcaster’s staff on Wednesday. He said his four years as head of news had been “incredibly tough but immensely rewarding”.

“Having said that, for reasons both professional and personal, now is the right time for me to move on and for someone else to take over the helm of the best news team in the country,” his email said.

There are reports the ABC is looking to replace Stevens with an outside. Marks – a former head of media giant Nine – said only that it had landed “someone of the highest calibre”.

The Guardian has named Simon Robinson, the London-based executive editor at global newswire Reuters, as Stevens’ successor.

Marks told senators on Thursday he had already interviewed candidates for the position, and he believed a “globally experienced executive is the right thing at this point in time for the ABC”.

“I’ve met a number of people over the years who might be opportunities for that role. I expect an announcement will be made imminently, and we will proceed with a candidate who I think has the potential to lead the organisation’s editorial into a bright future,” he said.

Senators also questioned the impartiality of the national broadcaster – which is consistently seen as one of Australia’s most trusted and beloved organisations, but faces increasing criticism from from conservative politicians.

Henderson said the description by ABC chair Kim Williams – who was absent from Thursday’s hearing despite a request for him to appear – of Israeli Prime Minister Benjamin Netanyahu as an “aberrant creature” was appalling.

“What sort of standard is that when you’ve got the chair of the ABC indulging in that sort of personal criticism?” she asked Marks.

Marks said Williams regretted his “less than desired” comments, which were his personal view and not that of the ABC.

Williams said the comments were made of Netanyahu’s leadership of Israel compared with past leaders, and should not be considered criticism of Israel.

Marks rejected suggestions of systemic bias.

-with AAP