Sutcliffe is the third senior figure to leave APCO in six months – following the recent departures of Darren Murphy and Andrew Escott.
Sources said Sutcliffe had been put on gardening leave after informing bosses of his decision.
APCO MD Simon Miller said: ‘He wanted to leave and explore career opportunities elsewhere.’ He would not comment on Sutcliffe’s next move.
Sutcliffe, a Conservative councillor, joined APCO six years ago and was promoted to associate director in 2005. His departure is a blow for the agency, coming weeks after associate manager Andrew Escott left to become head of commercial relations at the NHS Confederation.
Early this year, director Darren Murphy quit the agency to become head of government relations and external affairs at AstraZeneca.