Barnet have reported Notts County to the Football League and Football Association following boss Martin Allen's defection to Meadow Lane.
Allen left Underhill after only 19 days in charge to take over at the League One strugglers on a one-year deal.
Barnet, who are battling to stay in League Two, are seeking compensation from the Magpies for Allen's services.
The Bees claim Notts County only made contact once Allen told Barnet chairman Tony Kleanthous he was leaving.
The statement said suggestions that Allen, who was in his second spell in charge of the Bees, did not have a contract were "palpably nonsensical".
Kleanthous said: "We agreed a deal with him until the end of the season and we helped and supported him throughout.
"I told him that we were prepared to offer a new long-term deal that would certainly have provided him with a comfortable six-figure living but he made it clear that he wanted a chance to manage a team in League One next season.
"He said he wanted to take this opportunity despite the perfect happy working environment which we provided for him at Barnet FC."