Earlier this month, new team boss Eric Boullier said the matter is "in the hands of our lawyers", after Red Bull announced it had successfully wooed Dan Fallows back to Milton Keynes.
Late last year, we reported that as well as Red Bull's aerodynamics chief Peter Prodromou, McLaren has also signed his 'deputy', Fallows.
But just as Fallows was ending his 'gardening leave' and due to start work at McLaren, Red Bull announced that he has in fact returned to work as the reigning world champions' newly-promoted 'head of aerodynamics'.
McLaren, however, insists it has a "legally binding contract" with Fallows.
"We regard this turn of events as completely unacceptable," Dennis, who revealed that Fallows had even moved to Surrey prior to returning to Red Bull, told us in a statement from Shanghai.
"He'd got no lawful right to change his mind in that way, because he'd already accepted our offer of employment and had already signed a contract in recognition of that," he insisted.
"Not surprisingly, when he failed to start work on the start date we'd agreed on, we called, texted and emailed him, but got no response.
"It was only when he was belatedly revealed via press release as Red Bull's head of aerodynamics that we finally understood what had happened.
"As a result of all of this, McLaren will probably have no realistic option other than to instigate a High Court action against Red Bull," Dennis confirmed.
Red Bull boss Christian Horner reacted to Dennis' comments on Saturday by saying the team will "vigorously" defend its re-employment of Fallows.
"We don't see there is any case to answer," he told Press Association.
"Perhaps Ron would have been better giving me a call."