Last month, Sampson accepted the job of customer relationship marketing director at ITV Sales, but because he had worked at the RAB for more than a decade and was resigning to go to a rival media company, his contract would have prevented him from joining for several months.
However, insiders suggest that ITV decided to put pressure on the RAB by threatening to scrap its advertising arrangement with the RAB so that it would allow him to start his new job sooner.
ITV operates a contra system with the radio stations, where it exchanges its own commercial airtime for access to radio airtime to run ads promoting its programmes.
It is understood that the RAB refused to bow to ITV's threat and that ITV will pay the RAB for breaching Sampson's contract. No date for Sampson's arrival at ITV Sales has been decided.