Prime Minister and Cabinet department secretary Martin Parkinson said Senate estimates hearings held an important role in government, but the regular hearings to grill ministers and senior public servants about their work could descend into political point scoring.

"Where it becomes problematic is when it moves from genuine efforts focused on improving public administration to simply trying to embarrass the government of the day," he said.

"This has been true for a long time. You understand why it's all about trying to embarrass the government of the day, but there are times when public servants sit there and think, 'we really don't need to be here, because we're simply bit players in this whole exercise and you're not actually interested in improving the quality of public administration'."

Government agencies had not moved far enough to keep pace with changes in public expectations about what services they delivered and how they engaged with people and listened to them, Dr Parkinson said.

The public service had also erred in how it had viewed other "disruptions", including eroding trust in government and changes in the global strategic balance.

"If you think about all of those things, what have we done as public services? We've responded to them as if they are incremental changes, and I actually think they are much more paradigm shifts and that's why I keep coming back and I use the word 'disruption' really as short hand for that," Dr Parkinson said.

Social media users regarded its platforms as a way to quickly enter conservations with other people, something the public service was yet to understand, he said.

"What've we essentially done? We've treated it as a post box, we've taken a message and shoved it down social media, out to you."