Sacked Perth shock jock Howard Sattler is suing 6PR over his dismissal this year for asking prime minister Julia Gillard if her long-time partner Tim Mathieson was gay.
Sattler lodged a writ with the Supreme Court on Friday, seeking unspecified damages.
It claims his actions during the July 13 interview were not serious enough to warrant his sacking and could have been rectified by an on-air apology.
The writ claims the interview was arranged on the basis it would be candid and that Ms Gillard "did not at the time or subsequently object" to the question.
Sattler began his interview by asking Ms Gillard about offensive references to her body on a Liberal-Nationals fundraiser menu, her religious beliefs and same-sex marriage.
He then asked if he could put rumours to her about Mr Mathieson's sexual orientation.
Ms Gillard said the rumours were absurd.
"But you hear it, he must be gay. He's a hairdresser," Sattler said.
Later he asked: "You can confirm that he's not?"
Sattler later apologised to those who thought he went too far but was suspended then sacked after public anger over his interview.
At the time, Premier Colin Barnett said Sattler's questions were clearly inappropriate and disrespectful to a prime minister and to a woman.
Melbourne radio presenter Derryn Hinch said Sattler was "a coward" and suggested Ms Gillard "should have leant across the desk and slapped him".
"This is just low-life stuff," Hinch said.
General manager of 6PR Martin Boylen announced the decision to sack Sattler after hours of crisis talks on the day after the interview.
He said Sattler's questioning was disrespectful to the office and the person of the prime minister and inappropriate.
Sattler, who has Parkinson's disease, still had six months of his contract to run.
The writ says he earned $190,000 in the first year of his contract, $195,000 in the second year and $100 for each live and recorded commercial he read.
In his claim, Sattler said he lost the balance of his salary, an expected three-year extension of his contract (based on a conversation with the 6PR managing director in November last year) and opportunities for alternative employment.