The council's regeneration director was one of the favourites to take over from chief executive David Henshaw and was a key negotiator on a number of major schemes, such as the Paradise Street and King's Dock developments.
His departure is yet another sign of a growing instability within the council and comes just months after a series of planning knock backs for large, privately funded projects (ajplus 23.08.05).
Frank McKenna, of lobby group Downtown Liverpool in Business, believes the move will further dent confidence in the city less than three years before it becomes Capital of Culture in 2008.
'Parker's departure is one that has to be taken seriously,' said McKenna. 'It is certainly not a positive thing.'
He added: 'In the current climate it adds further weight to the argument that the city council is in a state of drift. The whole thing has descended into a soap opera.'
McKenna, who admitted he would be sad to see Parker go, was also worried about how to fill the vacant position. He said: 'Who'd want the job? Anybody with the right experience will be looking at it and thinking it is probably not their best career option.'
Parker has been with Liverpool City Council since the late 1990s and will now take up a role at Manchester-based company Enterprise.