Declan Kidney's London Irish insist they will "consider all options" after Premiership rivals Gloucester announced the appointment of Exiles forwards coach George Skivington as their new head coach.
The Cherry and Whites had earlier announced Skivington as the replacement for Johan Ackermann, who ended his three-year tenure in the post last month to take a role at Japanese Top League side NTT DoCoMo Red Hurricanes.
Gloucester are in the process of overhauling their leadership set-up, with ex-Ireland international David Humphreys set to step aside as the club's director of rugby.
But the Exiles were not happy with Gloucester's appointment, suggesting they had breached the Premiership Rugby code of conduct regarding inducement and approaches to a coach.
The Exiles revealed Skivington (37) was under contract until the summer of 2021 and that there was no approach from Gloucester's management requesting permission to speak to the coach.
Chief executive Brian Facer said on the London Irish website: "To say we are disappointed with Gloucester's announcement is an understatement.
"George is well liked and respected, and it is understandable that we would not want to lose him, especially so close to the resumption of play after the lockdown. We also know that he is an ambitious young man who would relish the opportunity of being the head coach of a club someday.
"However, the protocols are clear that a club must be approached in writing when there are more than six months remaining on the relevant contract, regardless of whether it is a player or coach.
"George is under contract with London Irish until June 2021 and has not served us with the required notice period, nor have the terms of his contract been breached. More importantly, at no point have we received any proactive communication whatsoever from Gloucester.
"We therefore believe that Gloucester have breached the Premiership Rugby code of conduct regarding inducement and approaches to a contracted player, member of coaching staff and other contracted person.
"This is a most serious issue so, accordingly, we are reserving our rights to consider all our options under the Premiership Rugby governance protocols and other avenues of redress."
Kidney coached Munster to two European Cups and Ireland to a Grand Slam in 2009 and was appointed Director of Rugby with London Irish in 2018, with his former Ireland defence coach and Ulster DOR Les Kiss as head coach.
The newly-promoted Exiles, who also number former Ireland internationals Sean O'Brien and Paddy Jackson in their ranks, are eighth in the Premiership Rugby table ahead the competition's expected resumption in August.