McClaren, who had only been in charge since June, has had his tenure disrupted by fan protest and board disagreements. It is believed the final straw came when the board failed to secure the loan signings of two Premier League players due to their wage demands.
Since taking over, the former Middlesbrough and England boss has secured only eight points for a side that, in pre season, were touted as real promotion contenders. They have also failed to secure a win at the City Ground in five games and have conceded eight goals in two games following the Birmingham loss and the 5-1 demolition at the hands of Burnley in midweek.
Forest, who now sit fourth from bottom in the Championship, will be looking to attain the services of a new boss before the club returns to action following the international break.