McLaren is taking legal action against Mercedes in a dispute over a key staff member that it claims had agreed to join the Woking-based team.
As part of McLaren's effort to bolster its structure during its new era with Honda, the Woking-based has been on a recent recruitment drive this year.
It has emerged that one of the key personnel it had persuaded to join it was Mercedes' head of vehicle dynamics, Loic Serra.
But despite McLaren believing that Serra that signed a binding contract to join the outfit, it has subsequently emerged that he will not be moving and will now remain at Mercedes.
That has prompted a dispute between the two teams, with McLarensuspecting that Mercedes had enticed Serra to break what it believed was a binding contract.
Mercedes boss Toto Wolff did not wish to comment on the matter when contacted, but confirmed that Serra was remaining at the Brackley-based team.
A McLaren spokesman said: "The matter is subject to legal proceedings and we do not wish to comment until that process is complete."
Serra was head of vehicle performance at BMW Sauber from 2006 to 2010 before moving to Mercedes in 2010 as chief engineer of vehicle engineering. He was promoted to head of vehicle dynamics in 2013.
Disputes between teams over highly-rated staff have flared up in the past, with one of the most recent cases being in 2014, when McLaren began legal action against Red Bull.
At the time, McLaren believed it had a binding contract with aerodynamicist Dan Fallows – before he decided to remain at Red Bull.
McLaren felt that Red Bull had enticed Fallows to break his contract, but in the end the matter was sorted out of court following face-to-face talks between McLaren chief Ron Dennis and Red Bull boss Christian Horner.