Barking, Redbridge and Havering NHS Trust has been asked not to give any further information on its chief executive stepping down by the Strategic Health Authority.
A statement from the trust cited the reason for Mark Rees sudden departure as 'in light of the London health strategic plans and the objective to achieve foundation trust status, there now needs to be a commitment over the next five years to drive further changes.'
When asked to elaborate a trust spokesman said they were 'under strict instructions not to say anymore than what appeared on the statement'.
A spokesman from NHS London said they would not be adding to the trust's statement.
Mr Rees has left on Monday following more than four years at the helm of the trust.