Jeremy Hanson is being sued by ACT CFMEU secretary Dean Hall for allegedly defamatory comments he made in a talkback radio interview last year.

Lawyers for Mr Hall told the ACT Supreme Court they had been forced to launch separate applications to strike out the two main defences pleaded by Mr Hanson, the most recent being "manifestly defective; we would say untenable" and unlikely to succeed.

The lawyer said Mr Hanson's defence against the defamation claim had shifted between honest opinion and contextual truth, in that the comments made in the interview also carried other imputations that were true and did not harm Mr Hall's reputation.

Mr Hanson had been indemnified by the ACT taxpayer and it could foot the bill for a potential court hearing stretching up to 15 days, the court heard.

The lawyer said Mr Hanson was "quite happy" to continue the case "because he's not paying, the ACT taxpayer is paying".

Mr Hanson's lawyer accepted the pleadings in the most recent defence were inadequate but said the 15-day hearing estimate would include both evidence and submissions.

In March last year, Mr Hanson appeared on 2CC to discuss an agreement between UnionsACT and the ACT Government that gave unions a role in procurement decisions.

Mr Hanson labelled it "secret deal" and argued that it gave unions an effective veto power over government purchases.

Mr Hall alleges the then Liberals leader defamed him when he said: "Do we want people like Dean Hall, who runs the CFMEU, or others who potentially are facing charges or have been convicted of charges, ah, given access to, ah, company documents?"

Mr Hall launched civil action against both 2CC and Mr Hanson in the Supreme Court last June.

The station settled soon after, issuing an on-air apology and agreeing to a confidential payout.

But Mr Hall continued his case against Mr Hanson. The matter was ordered to mediation in July but the talks had failed, clearing the path for a court showdown.

Mr Hall's case argues Mr Hanson's remarks implied that the union boss was so untrustworthy or dishonest that he should not be given access to government tender documents, because he had either been convicted of, or was facing, criminal charges.

Mr Hall has been convicted only of drink driving, an offence more than a decade old, well before his tenure in the unions.

The defamation claim said that the remarks injured Mr Hall's reputation and he suffered loss and damage.

In his defence, Mr Hanson initially argued his words had been taken out of context and the comments should be read in the context of the entire interview.

He said the comments had not been defamatory and did not carry the imputations alleged by the union boss.

The case was adjourned to give Mr Hanson's lawyers time to file an amended defence. It returns to court in October.