The London office is now headed by Jonathan Hodgkinson, a former associate partner at Bell Pottinger who was appointed as MD at Prosek Partners last autumn, initially working under Waterworth.
Hodgkinson reports directly to managing partner Jennifer Prosek.
Waterworth was hired by Prosek in 2012 after leaving FTI Consulting, where he was the financial services practice lead.
Prosek confirmed that Waterworth has left the company, but declined to comment further.
The predominantly US-based Prosek Partners also has offices in New York, Los Angeles and Connecticut, and handles PR for clients from across the b2b, fintech and asset management sectors.