Cameron is understood to have departed from the City agency in recent weeks, a move that is said to have been mutually agreed.
He joined the agency in March 2010 after establishing his own firm, Westcliff Strategic. Formerly he was a partner at Brunswick Group, working in its London and Johannesburg offices.
Cameron co-led Powerscourt's financial group and capital markets practice. It is thought that Cameron may now look to establish a new comms venture.
Powerscourt founder Rory Godson confirmed Cameron's departure and said he had 'been hugely helpful through a period of tremendous growth'.
Powerscourt is not understood to be seeking a direct replacement in the COO role.
Earlier this year, the agency hired former FD (now FTI Strategic Comms) MD Giles Sanderson as a partner to handle clients and drive new business. The agency also promoted Victoria Palmer-Moore to the role of partner.
Powescourt has been involved with a number of high-profile clients in recent times, winning a mandate to work with NewsCorp's Management Standards Committee in the summer and working for BP and Prudential.