Christian Porter twice offered to settle defamation proceedings with the ABC, before finally discontinuing proceedings last week, in an agreement that saw his law firm receive $100,000 in mediation-related costs from the public broadcaster.

At a Senate estimates hearing where Coalition senators largely ventilated outrage at tweets by ABC journalists, the broadcaster’s managing director David Anderson shed more light on the nature of the settlement with Porter.

At an additional hearing this morning, Anderson revealed Porter had made his initial without-prejudice offer in March, before the ABC filed its defence. The former attorney-general amended this offer days after the broadcaster’s defence was filed in May.

The parties later proceeded to mediation, and the settlement which was reached last week saw the broadcaster pay $100,000 in mediation costs to Porter’s lawyers, Company (Giles). That was still a substantially lower sum than the $1-1.5 million Anderson estimated a trial might have cost the broadcaster. The ABC had paid $680,000 in legal costs defending Porter’s claim before the settlement.

Anderson’s evidence hosed down claims made by Porter, and some by media commentators, that the settlement, made in the most plaintiff-friendly defamation jurisdiction in the world, was a win for the former attorney-general. A defiant Porter last week claimed the ABC had been “forced to say they regret the article”.

But Anderson reiterated that all the ABC had done was issue an editorial note, accepting some readers had misinterpreted the article as an accusation of guilt against Porter.

“I will say that the matter has been settled,” Anderson said.

“I will say that the ABC has not issued an apology. The ABC stands by its journalism.”

Later, the managing director was put through the wringer by Liberal senators over the broadcaster’s social media policy, a common sore point for conservatives. Following questions from Liberal Senator James Paterson, Anderson said he was “concerned” about a tweet from Four Corners executive producer Sally Neighbour following the settlement.

Paterson and WA Liberal Senator Ben Small also highlighted a series of tweets, mostly gloating about Porter’s defamation backdown, as evidence of systemic bias, and inappropriate social media use at the public broadcaster.

Meanwhile, Liberal Senator Sarah Henderson pointed to the BBC’s tough new social media guidelines, which prohibit employees from posting personal opinions about “public policy, politics, or controversial subjects”, arguing the broadcaster’s current policing of its employees tweeting was “woefully inadequate”.

Anderson said the ABC’s approach allowed employees to be reprimanded — and in serious cases, have their employment terminated — but that the organisation did not want ABC employees restricted from posting about politics and public policy.

“They’re fairly broad, Senator. I wouldn’t issue a blanket ban on those topics for anyone,” he said.