The dispute is understood to have centred on the future direction of the agency, with Pemsel, the chief executive, and Stanners, the creative director and Pemsel's wife, disagreeing with Law, the chairman of the agency.
Sources suggest that the relationship between Law, the former St Luke's founder, and Pemsel had broken down, with the result that Pemsel has left the agency and Stanners has tendered her resignation. Boymeetsgirl's partnership structure means the partners cannot fire each other.
The row echoes the clashes at St Luke's last year, when Law and Stanners were ousted from the agency after falling out with its two managing directors.
On the breakdown of the Boymeetsgirl partnership, Law said: "To my knowledge and as far as I understand, they (Pemsel and Stanners) are staying in the partnership and operating as they have been, with David as the chief executive and Kate as the creative director; we remain as we are."
Boymeetsgirl, which is backed by Interpublic and Springer & Jacoby, handles advertising for DaimlerChrysler, Total petrol stations and Disney's DVDs and videos. It is positioned as a non-advertising-led creative services agency with a 360-degree take on creativity. It claims billings of £60 million.
IPG, Stanners and Pemsel all declined to comment.