The resignation email, sent this morning (25 September) by Kieran Allen, a senior account manager at MEC, listed a series of grievances against his manager.
The email was quickly disseminated around rival agencies and details of it trended on Twitter. A full transcript of the email was also published on Twitter by Loaded Magazine @loadedmag.
In a statement the agency, which is led by chief executive Steve Hatch, said: "We are sad that one of our employees has chosen to share their personal views in such a public way and has left the company with such bad feeling. We are taking this issue seriously though given the highly personal nature of the email, we cannot comment further."
This article was first published on campaignlive.co.uk