Folau, 30, is suing RA and the NSW Waratahs for unlawful termination under the Fair Work Act, arguing RA tore up his four-year, multimillion-dollar contract was torn up because of his religion.

His legal team, led by Melbourne lawyer George Haros, filed the claim in the Federal Circuit Court late on Wednesday, after mediation failed before the Fair Work Commission in June.

The development has raised the prospect of a directions hearing taking place while Australia is in the thick of a tough World Cup campaign in Japan.

It would be nightmarish timing for RA, with the case potentially overshadowing the campaign and disrupting the organisation's plans to use the sport's biggest four-yearly event to reboot its popularity in Australia.

"Unfortunately, our conciliation before the Fair Work Commission did not resolve the matters between us and I have been left with no choice but to commence court action," Folau said in a statement on Thursday.

RA has 28 days to file its response to Folau's claim in court, after which the court would set a date for a directions hearing, a process that would see legal representatives for both parties - but not Folau or any RA staff - appear in court. That could take place anywhere from two to six weeks after RA lodges its response.

With the World Cup starting in 50 days and Australia playing Fiji in their opening pool game on September 21, Rugby Australia boss Raelene Castle could have her attentions divided between the Wallabies in Japan and what looms as a costly legal battle in Melbourne.

The Federal Circuit Court is commonly understood to be a quicker and marginally cheaper avenue to go down than the Federal Court, although both courts share the same jurisdiction and hear cases on the same areas of law, including industrial, migration, bankruptcy and consumer law.

The directions hearing would end in one of two ways. A judge could direct the parties to undertake mediation, or move straight to a trial.

In the quickest possible time frame, a trial could take place before the end of the year, setting the stage for a high-profile test case on the rights of employers to enforce employment contracts.

RA terminated Folau's multimillion-dollar contract in May after the dual international made a social media post in which he paraphrased a Bible passage, saying "drunks, homosexuals, adulterers, liars, fornicators, thieves, atheists and idolaters" would go to hell unless they repented.

Folau, 30, is seeking $10 million in damages from RA and wants his contract reinstated. He is represented by solicitor George Haros and barrister Stuart Wood QC.

RA has retained top firm Herbert Smith Freehills but is yet to engage a barrister. Justin Gleeson SC acted for the organisation during the code of conduct hearing that ultimately ruled in favour of RA.

More than 20,000 people recently donated about $2.2 million to help fund Folau's legal battle via a campaign page set up by the Australian Christian Lobby.

The ACL effort replaced an earlier campaign on GoFundMe, which was taken down by the platform for breaching its service guidelines.

Folau thanked his many supporters in his statement on Thursday.

"I have been blessed to have received the support of tens of thousands of Australians throughout my journey, and I want to say thank you to everyone who has offered their prayers and support. It has meant so much to (wife) Maria and me over the last few months and gives us strength for the road ahead," he said.

Section 772 Employment not to be terminated on certain grounds

(1) An employer must not terminate an employee's employment for one or more of the following reasons, or for reasons including one or more of the following reasons:

(a) temporary absence from work because of illness or injury of a kind prescribed by the regulations;

(b) trade union membership or participation in trade union activities outside working hours or, with the employer's consent, during working hours;

(c) nonmembership of a trade union;

(d) seeking office as, or acting or having acted in the capacity of, a representative of employees;

(e) the filing of a complaint, or the participation in proceedings, against an employer involving alleged violation of laws or regulations or recourse to competent administrative authorities;

(f) race, colour, sex, sexual orientation, age, physical or mental disability, marital status, family or carer's responsibilities, pregnancy, religion, political opinion, national extraction or social origin;

(g) absence from work during maternity leave or other parental leave;

(h) temporary absence from work for the purpose of engaging in a voluntary emergency management activity, where the absence is reasonable having regard to all the circumstances.