McLaren boss Ron Dennis is planning High Court action against rivals Red Bull over a member of their technical staff who recently moved back to the Austrian team.
The dispute surrounds Dan Fallows, who left Red Bull to join McLaren, only to recently return to his former employers as their head of aerodynamics.
Dennis insists Fallows signed a legally-binding contract that was due to commence in early March, only for Fallows to perform a dramatic U-turn and restart at Red Bull.
"To be honest that's completely unacceptable to us," McLaren group chief executive Dennis told Autosport.
"Just days before Fallows' McLaren start date - and despite having signed a legally-binding contract with McLaren, being on gardening leave from Red Bull, and moving to a new home near Woking - he suddenly informed us that he no longer wanted to work for us.
"The problem was, he had no legal basis on which to make that U-turn because he'd already formally accepted, and contracted himself to, our offer of employment."
Opting to now address the matter further, Dennis added: "Sadly, it's now likely that McLaren will have no alternative other than to pursue a High Court action against Red Bull, which will ask very serious questions as to that team's integrity and sense of fair play."
Dennis claims all attempts to contact Fallows prior to Red Bull last week announcing his return were "met with stony silence".
Red Bull team principal Christian Horner has been left exasperated by Dennis' stance, insisting Fallows' re-employment is all above board.
Horner told Press Association Sport: "I'm disappointed in Ron's comments.
"The matter is now in the hands of the lawyers, but this is something we will defend vigorously. We don't see there is any case to answer.
"It's disappointing McLaren has pursued this route. Perhaps Ron would have been better giving me a call."