The backbencher was kicked out of the LNP this month following allegations of "disgusting behaviour" towards an 18-year-old, which he strenuously denied.

Last sitting week, LNP manager of opposition business Jarrod Bleijie used parliamentary privilege to unleash on Mr Costigan, labelling him "lazy" and detailing five separate harassment complaints.

Mr Costigan was absent two weeks ago but returned to Parliament on Tuesday, sitting on the crossbench for the first time. He slammed what he described as a "disgraceful attack" by the LNP.

"The comments made in this place by members of the opposition made me sick," he said.

"They were misleading, exaggerated, deceptive, extremely hurtful and politically loaded, to say the least."

Mr Costigan said he did not believe he had done anything wrong in relation to "what supposedly happened" in the alleged incident with an 18-year-old in Victoria.

"I shall be taking the strongest possible action, Mr Speaker, against the person or persons involved in what can only be described as a malicious attempt at destroying someone's career and gleefully accepted by the LNP hierarchy," he said.

Mr Costigan said it was "no secret [that] certain people within the LNP wanted us gone, and for some time".

"Many constituents of mine and certainly supporters, Mr Speaker, will remember the white-anting before that bitter preselection battle in Proserpine in November 2014," he said.

"And despite two more election wins since then, those white ants have come back."

Mr Costigan said his speech in November last year, when he criticised the LNP for its "inability to campaign effectively in north Queensland", went down "like a lead balloon" with LNP leader Deb Frecklington and the "faceless men" in the party.

He said the events of recent weeks had knocked him, his family and loved ones around.

"So much for bullying in the workplace," he said.

"I will continue to fight for my constituents, regardless of what has happened and where I sit in this chamber."

The member for Whitsunday said he had never proclaimed to be perfect, while vowing to contest the next state election due in October 2020.

"If I have offended anyone, I most sincerely apologise," he said.

"That said, I will take up the fight to clear my name, Mr Speaker, and stare down anyone who tries to tarnish it.

"I have no intention of going anywhere.

"And I look forward to taking the fight up to the major two parties at the next state election."

Mr Costigan also said almost 40 members had resigned from the LNP between Mackay and Bowen.

LNP leader Deb Frecklington said she stood by the action she took in relation to Mr Costigan.

"He didn't meet my standards and that's why he's no longer a member of my team," she said.

Asked if the LNP had a candidate for Whitsunday, Ms Frecklington said: "I'm sure we'll have a candidate for Whitsunday."