His death was announced by Worcestershire County Council, where he was interim chief executive, on Thursday evening.
The notice read: 'It is with deep sadness we announce that Steve Stewart, interim chief executive of Worcestershire County Council, has passed away. Steve joined the council in May last year, making a big contribution during his time in the county. Our thoughts are with his family at this very sad time.'
In 2008, Mr Stewart was appointed to lead Northumberland County Council into a unitary authority, overseeing the merging of the six district councils - Blyth Valley, Wansbeck, Castle Morpeth, Tynedale, Alnwick and Berwick-upon-Tweed - and the existing county council in April 2009.
He was previously assistant chief executive at Northamptonshire County Council and also held top roles at councils in Wakefield and Leeds, Sunderland and York.
He opted to leave Northumberland council in November 2013 after the then Labour-led authority announced consultation plans which would see the role axed.
The Northumberland Conservatives group said: "Steve Stewart was an effective council officer and a character known to many for his good humour and engaging style while he was chief executive at Northumberland County Council. Our thoughts are with his family at this difficult time."
Nigel Walsh, the culture, heritage and libraries service manager with Northumberland County Council, who worked with Steve, has commented: "Sad to hear this - he was a nice guy and strong supporter of culture. Thoughts to his family."