Former parliamentary speaker Peter Slipper says he feels vindicated by the Federal Court's decision to dismiss a sexual harassment case against him.

Justice Steven Rares ruled the case brought against Mr Slipper by one of his staff members was an "abuse of process", declaring that its predominant purpose was to cause "significant public, reputational and political damage".

"To allow these proceedings to remain in the court would bring the administration of justice into disrepute among right-thinking people and would be manifestly unfair to Mr Slipper," he said in his judgment.

Mr Slipper has welcomed today's ruling, saying he has always maintained the case was designed to damage his reputation and political career, as well as advancing the interests of the Coalition.

"I feel vindicated by today's judgment," he said in a statement.

"The past eight months have been extremely traumatic for my wife, family and me.

"I thank my wife, family, staff and friends for their support during this extraordinarily difficult time."

Mr Slipper stood aside from his post in April after James Ashby accused him of harassment, including that he made unwanted sexual comments and encouraged him to shower with the door open while staying at the Speaker's Canberra flat.

Speaking outside the court, Mr Ashby said he was "extremely disappointed" with the Federal Court's decision and indicated he would lodge an appeal.

"This has been a very harrowing time for me and my family, my friends and supporters," he told reporters.

"We first filed my sexual harassment complaint against Mr Slipper back on April 20 and that is almost eight months ago - eight months.

"Since that date no evidence at all has been heard of my substantive complaint against the former Speaker that he sexually harassed me.

"There's been a determined campaign to try and prevent the substantive allegations being heard and judged in open court and to put me to the maximum cost in pursuing justice."

Sorry, this video has expired James Ashby reacts to the decision to throw the case out of court

In his written judgment, Justice Rares said he believed Mr Ashby and fellow staff member Karen Doane had been working with former Howard government minister Mal Brough "to cause Mr Slipper as much political and public damage as they could inflict on him".

He described the pair's behaviour as "acts of calculated disloyalty".

"Once they had decided on their course of action, Mr Ashby and Ms Doane did not go straight to see a lawyer to air any concerns about any legal wrongs that either may have suffered," Justice Rares wrote.

"Instead, Mr Ashby or Ms Doane contacted Mr Brough and they began working with him and (News Limited journalist) Steve Lewis."

In July, Mr Brough won a preselection contest to run as the Liberal National Party's (LNP) candidate in Mr Slipper's Sunshine Coast electorate of Fisher.

Labor frontbencher Mark Dreyfus has called on the LNP to disendorse Mr Brough, describing his position as "untenable".

"The Liberal National Party of Queensland should hang their heads in shame for even having endorsed him as a candidate," he told reporters in Canberra.

However, the party appears to be standing by its candidate, with a statement from the LNP this afternoon saying Mr Brough "will provide a strong voice for the people of Fisher".

Mr Brough also released a statement in response to the court's ruling.

"I reiterate that I have at all times acted appropriately in relation to this matter and given the decision is subject to appeal I do not intend to make further comment."

'Scandalous'

As part of his original claim, Mr Ashby also accused Mr Slipper of misusing taxi vouchers. The Federal Police have investigated the allegations and referred the matter to the Commonwealth Director of Public Prosecutions (CDPP).

A spokeswoman for the CDPP says the matter is still being "actively considering" in conjunction with the AFP.

Justice Rares has criticised Mr Ashby's decision to include the accusations in his claim, saying that in his opinion their "predominant purpose" was to assist in the political attack on Mr Slipper.

"This is emphasised by his decision to include the assertion that he intended to report the matter to the Australian Federal Police," he wrote.

He also criticised Mr Ashby for including "scandalous and irrelevant" references in his originating application that Mr Slipper had a sexual relationship with a male staff member in 2003, and that it had been recorded on video.

"The 2003 allegations had nothing to do with Mr Ashby's complaint that Mr Slipper sexually harassed him," Justice Rares wrote, declaring that the purpose of its inclusion was to attract significant adverse publicity in the media.

"I am of opinion that Mr Ashby's and (his lawyer, Michael Harmer) Mr Harmer's pleading of 2003 allegations was scandalous, oppressive and vexatious and an abuse of Mr Harmer's professional obligations to the court as a lawyer."

'Disappointed'

In a statement, Mr Harmer says he is "shocked and disappointed" by the court's decision and has moved to defend his firm's reputation.

"We will argue strongly on appeal that the conclusions in his Honour's judgment made about our conduct of the case are simply not justified by the evidence," he said in a statement issued through the same person who has been providing media advice to Mr Ashby.

"Neither myself, nor this firm, are part of any conspiracy."

Justice Rares has ordered Mr Ashby pay Mr Slipper's legal costs.

Mr Slipper quit the LNP late last year after accepting the Government's nomination for Speaker of the House of Representatives.

He resigned from his position in October after it emerged that he had used vulgar euphemisms for female genitalia in a text message.

In another message, he referred to Liberal frontbencher Sophie Mirabella as an "ignorant botch" (sic), a term Mr Ashby had used in a previous text message to the Speaker.

In standing down, he apologised for his use of language.