Fairfax Media journalist Sean Nicholls has told a defamation trial his editor's wish to have a story on Joe Hockey "nailed to the cross in more ways than one" was not a desire to "crucify" the Treasurer but a reference to "nailing the facts".

Giving evidence on the third day of the Federal Court hearing, Nicholls said the headline "Treasurer for sale" was "very much" a fair summary of an article he wrote about Mr Hockey on May 5, 2014.

Nicholls, the Herald's state political editor, said his interest in Liberal fundraising body the North Sydney Forum was piqued when Mr Hockey reacted very strongly to an incorrect March 21 report that he had refunded political donations to a company involved in a corruption inquiry, when it was the forum in his electorate which had repaid the money.

The court heard Herald editor-in-chief Darren Goodsir emailed Nicholls on March 27, 2014 saying: "...given what Andrew [Holden, editor-in-chief of The Age] and I endured last week with Hockey, I want to have this nailed to the cross in more ways than one … keep digging Sean… I have long dreamed (well, only since last Friday), of a headline that screams: Sloppy Joe! I think we are not far off, but perhaps even more serious than that."

In cross-examination Mr Hockey's barrister Bruce McClintock SC put to Nicholls: "Mr Goodsir was suggesting that you crucify my client?"

Nicholls replied: "That's certainly not what I took from it".

He added he "didn't quite understand" the "mixed metaphor" but he took Goodsir's email to mean he should ensure his investigation of the forum was "meticulously accurate" and he should have the "facts nailed down tight".

Asked about the "Sloppy Joe" line, Nicholls said: "This was an editor-in-chief seeking to gee up his troops."

In a later email, Goodsir wrote: "I'll be back on Mon 28 and want to be in a spot to launch our dirt on Hockey then. This one ain't over yet."

Nicholls said the term "dirt" was common journalistic parlance for investigating someone. He agreed the second sentence was a reference to the apology and correction Fairfax published over the March 21 article, written by Canberra-based chief political correspondent Mark Kenny.

The Treasurer says the May 5 articles, which suggested he provided "privileged access" to members of the forum who paid up to $22,000 a year in membership fees, conveyed that he is corrupt and "accepted bribes paid to influence the decisions he made" as Treasurer.

Further, he claims Fairfax Media acted maliciously because it was aggrieved at having to publish the correction. Fairfax denies the claims.

In the course of investigating the forum Nicholls sent Mr Hockey's press secretary, Gemma Daley, a list of 13 questions on the Friday before the article was published in the Herald, The Age and The Canberra Times.

In return, he received a two-line response from Ms Daley that said: "Questions about the function and administration of the North Sydney Forum should be addressed to them. The Treasurer's diary is confidential."

Mr Hockey's case is that he would have sent a different answer had he known the contents of the article.

Mr McClintock said the list of questions made no specific reference to the allegations that topped the story, namely that Mr Hockey had granted "privileged access to a select group including business people and industry lobbyists in return for tens of thousands of dollars in donations".

Nicholls agreed but said the questions, combined with conversations he had had with Mr Hockey's office and members of the forum, clearly indicated the angle he was pursuing.

"It would have been blindingly obvious to any media or political professional," Nicholls said.

Later on Wednesday, Kenny was asked about his analysis piece headlined "The price tag on Joe Hockey", which opened with the sentence, "Nobody is suggesting Joe Hockey is corrupt."

Kenny rejected Mr McClintock's claim that the balance of the article conveyed the opposite, and said there was no question of Mr Hockey's integrity. However, the system of political donations in Australia warranted scrutiny.

"Absolute confidence only comes with absolute transparency," he said.

Mr McClintock asked how the forum was any different to other events attended by Mr Hockey such as the National Press Club, of which Kenny is a director.

"One of them is one of the most open forums in the country; the other one is totally opaque," Kenny replied.

Goodsir will give evidence on Thursday.