Former Seven Network producer Taylor Auerbach has begun giving evidence about bombshell allegations he made about the network's engagement with former Liberal staffer Bruce Lehrmann.

The former producer of Seven's Spotlight program is appearing before the Federal Court today as the key witness in additional evidence in Network Ten's defence of a defamation claim brought by Mr Lehrmann.

He was questioned about a night in Sydney when he dined with Bruce Lehrmann at a Sydney restaurant for the purpose of securing an exclusive interview for the program.

It was for the purpose of "building up a rapport, trying to build trust, some kind of relationship".

Mr Auerbach said Mr Lehrmann had bought cocaine and later ordered sex workers to the Meriton hotel in Sydney CBD, which Mr Auerbach said had been paid for by Seven.

Mr Auerbach told the court he began texting his boss, former executive producer Steve Jackson, that "Bruce was on the warpath again".

"I think I used the words 'this is f***ed'," he told the court.

He told the court that he tendered his resignation with Seven the day after the incident in a letter to the network.

"That morning was the worst morning of my life," he said.

But Mr Auerbach said his resignation was not accepted, and he was instead offered a promotion and a pay rise.

Former producer denies trying to 'destroy' those connected to Seven

Lawyers for Mr Lehrmann questioned Mr Auerbach about claims that he was later instructed by Mr Jackson and an external lawyer to delete communications he had with Mr Lehrmann.

"The allegation you make against the lawyer …. is incredibly serious," barrister Matthew Richardson said.

Mr Richardson suggested to Mr Auerbach that the lawyer "never so much as hinted" he should "do anything of the kind".

"That's completely incorrect," Mr Auerbach replied.

Mr Auerbach agreed that he had threatened to appear at Seven's annual general meeting and make claims that would "embarrass" the network, but denied suggestions that he was willing to "say anything, no matter how false, to damage people who are employed by Channel Seven".

He said he had contacted The Walkley Foundation about his "concerns" that Spotlight's interview with Mr Lehrmann had been nominated for an award.

"I was not proud of that story," Mr Auerbach told the court.

Ten aiming to use new evidence to trap Bruce Lehrmann in a falsehood

Mr Lehrmann is suing Ten and Lisa Wilkinson over an interview with Brittany Higgins on Ten's The Project, after his criminal trial for her alleged rape was abandoned with no findings against him.

Justice Michael Lee was due to hand down his judgement today but the case was re-opened after Ten won its bid to allow Mr Auerbach to give evidence.

Network Ten will attempt to argue that the evidence raises questions about Mr Lehrmann's credibility.

The court heard Mr Auerbach will testify that Mr Lehrmann provided the material, though he has denied doing so.

If Ten's arguments are accepted, Justice Lee may also have to decide whether Mr Lehrmann's conduct was an abuse of process.

Earlier, Seven Network was questioned about why it had only produced one page of communications between network employees and Mr Lehrmann relating to his appearance on the Spotlight program last year.