Sugden is believed to have lost the backing of the firm’s lending banks who are owed the first £30m tranche of debt payments in March.
Sugden’s departure is the latest blow to the consultant which has been hit by a series of profit warnings and a dramatic dive in its share price.
He is believed to have wanted the chairman’s role on a permanent basis but the move was blocked by bankers.
Former BBC Trust chairman Sir Michael Lyons has now been parachuted in as interim chairman while the search for a permanent figurehead begins.
Mouchel confirmed Sugden had resigned following “further discussions with the board and other key parties about the best way to secure Mouchel’s future”.
The firm’s statement added: “The lending banks have informed the board that they are fully supportive of the board and its executive team which believes that Mouchel has strong and valuable businesses which need to be supported by a stable, long-term financial structure.
“Sir Michael Lyons, senior independent director, is leading the search for a new external chairman and will chair the board while a new chairman is sought.”
Sugden started his brief stint in charge last Thursday when chairman Bo Lerenius and chief executive Richard Cuthbert left following the profits warning.
Sugden said on his appointment: “In my role I will be focused on ensuring Mouchel has a clear strategy and a sound financial structure, whilst building our relationships with our shareholders and our banks.”
The Mouchel statement added: “Executive directors Grant Rumbles and Rod Harris remain focused on the steps necessary to secure the future of the company and they enjoy the full support and confidence of the board and its lenders.”