Brabin was the 2008/09 Blue Square Premier manager of the season
Cambridge manager Gary Brabin has been sacked following a deterioration of his relationship with the U's board.
A club statement read: "Gary Brabin has been relieved of his duties as first-team manager with immediate effect.
"Assistant manager Paul Carden has been asked to take charge of first-team affairs in the immediate future."
Brabin, 38, left Southport to take over at United last summer and led them to the Blue Square Premier play-off final, which they lost 2-0 to Torquay.
"There have been a number of issues between the board and the manager in recent months," continued the club statement, "culminating in a position where it has become untenable for the board and manager to work together.
"The board will now discuss the best way forward for the club and begin the process of recruiting a new manager."
In May, the U's gave Brabin permission to speak to a Football League club, after he was linked with the vacant Blackpool job.
He was named Blue Square Premier manager of the season in June.
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