The Public Service Commission is revisiting its past advice to public servants in the wake of ongoing confusion over what type of public comments are acceptable, especially on Facebook and Twitter.

Federal law requires public servants to be "impartial". The commission's current guidance says this means staff should avoid "harsh or extreme" criticisms of any politician, political party or policy, if the comment could raise doubts about their impartiality.

The advice applies regardless of whether public servants' comments are made outside of work or even anonymously – for example, using an alias on an internet forum.

However, Public Service Commissioner John Lloyd acknowledged that many public servants wanted "the right to make comment on issues of public interest in their own time".

"This of course raises the question as to what it means to be an impartial public servant," Mr Lloyd said.

"The spread of social media and the ease of its use reinforces the need for clear guidance about what can be said and what can't be said."

Several high-profile cases in recent years have failed to clarify the conflict between public servants' duty to be impartial and their freedom of political communication, an implied right in the constitution.

In 2010, The Australian newspaper outed then public servant Greg Jericho as the anonymous author of political blog Grog's Gamut. Dr Jericho underwent a lengthy misconduct investigation though there was no finding against him.

In 2013, the Immigration Department sacked one of its communications staff, Michaela Banerji, who had criticised refugee policy via a pseudonymous Twitter account.

Last year, Centrelink officer Daniel Starr was dismissed after his employer discovered he commented regularly on an internet forum that helped welfare recipients. Most of Mr Starr's comments were useful advice – he even corrected wrong information posted by Centrelink – though several of his comments were rude.

He won his job back earlier this year after appealing against his sacking.

Mr Lloyd said "there's a legitimate question as to whether we [the commission] have the balance right in the guidance that we give".

"Even if the policy is right, are the words right? Can we make it easier to understand? Can we give you, and agencies, more clarity and certainty?

"The answers to these questions are not straightforward."

One high-profile former senior public servant, Sandi Logan, warned against changing the policy on Wednesday.

Mr Logan, the Immigration Department's ex-spokesman who was involved in the sacking of Ms Banerji, tweeted:

The government has asked bureaucrats and the public to post their thoughts on an open forum on the commission's website.

It wants ideas about whether: