Essendon coach Mark Thompson fully supports his club's decision to take legal action against ASADA, imploring Bombers supporters to "back our boys" during another difficult period for the club.

Club chairman Paul Little confirmed on Friday afternoon that Essendon had filed an application in the Federal Court against ASADA, alleging its joint investigation with the AFL into the club was unlawful and in breach of the ASADA act. 

Thompson said legal action was a necessary step in putting the players' welfare first, just days after 34 players were issued show-cause notices by ASADA.

"At long last, after all this time, we're supporting the players because everyone's been saying the players have been the number one priority," Thompson said on Saturday morning.

"Well now they are and let's try to work for them. You should be reporting that way. If it was your brother or sister or son or daughter, how would you feel?

"Back our boys".

On hearing that final comment, the few hundred Bombers supporters in attendance broke out into a lengthy applause and the press conference was declared over.

Earlier, Thompson revealed he had spoken to suspended coach James Hird, currently in France, on Friday night.

Hird, who is also bringing his own action against ASADA, is still hoping to return to the coaching chair as of next season when his 12 month suspension for bringing the game into disrepute expires on August 25.

It was the first conversation the pair have had all year, according to Thompson.

"He just basically asked about the players, how they were feeling and he asked more about the team and how they've been going," Thompson said.

"It wasn't a long conversation."

More to come.