Details emerged this week over legal proceedings lodged by Stanbrook, who left DLA after less than a year in the role of managing director of the public affairs division.
It is understood he is suing for alleged breach of contract. Neither Stanbrook or DLA would comment on specifics of the litigation, but both confirmed proceedings had been issued by Stanbrook.
DLA will not be recruiting a replacement for the MD role, which was created only a year ago.
The news comes as Stanbrook announces his appointment as MD of Brussels-based public affairs shop PRM European Lobbyists.
PRM chief executive Tom McClay and chairman Lord Plumb created the role to match the agency's growth, they said.
Launched three years ago, PRM lists past and present clients including Consignia, British Veterinary Association and a number of developing world governments.
Stanbrook said PRM aims to bring law and PA closer together.
'There's still a great opportunity in Brussels for what may be called a Washington-style service,' he added.
PRM, which stands for Plumb Ramsay McClay, now employs a team of 12, including three executive directors.