Rob Messenger and his wife Fern worked for Ms Lambie between 2014 and 2017, managing the senator's offices and staff in Burnie and Canberra.

They were sacked in 2017 for serious misconduct after Mr Messenger sent a letter to then-prime minister Malcolm Turnbull about Senator Lambie's alleged inappropriate workplace behaviour.

In the letter, he claimed credit for many of Senator Lambie's contributions to parliament and ridiculed her speaking and reading skills.

He claimed he worked unreasonable hours, was sworn at and bullied, and said he would field phone calls from war veterans without appropriate training or skills.

Senator Lambie said the letter was demeaning and believed Mr Messenger was trying to shame and belittle her.

When she found out the letter had been sent to Mr Turnbull, she said it represented a breakdown of employer-employee trust.

"I just thought, how demeaning, and why would you send it to a prime minister? I found it absolutely disgusting," she told the court.

"There was no trust ... there was only one thing left, and that was to dismiss them."

The Federal Court on Friday found Senator Lambie's decision to terminate Mr Messenger's employment was fair and not controversial.

"She was, to say the least, unimpressed that the Messengers had seen fit to air the unmistakably ridiculing and demeaning insults that we littered throughout the correspondence to the office of the prime minister," Justice John Snaden said in his decision.

"One need only read the correspondence to understand why or how she might have formed that state of mind."

Further, Judge Snaden said the Messengers had tried to use the court trial to further damage Senator Lambie's reputation.

"Despite repeated warnings, the Messengers appeared at times determined to turn the trial into some kind of broad-ranging judicial inquiry into Senator Lambie's character," he said.

Both applications for unfair dismissal were rejected.

Australian Associated Press