Walter Smith has resigned as Rangers chairman and left the board amid a bitter struggle for power at Ibrox.
Smith has stepped down three days after former chief executive Charles Green returned to the club as a consultant and issued a public warning to manager Ally McCoist over his long-term future.
In a statement to the London Stock Exchange, the club said: "Rangers announces that Walter Smith has today resigned from his position as chairman and a director of the company with immediate effect."
Smith joined the board in November last year in what was a huge coup for Green, who had rejected a bid from a consortium led by the former Rangers manager immediately after buying the liquidation-bound club's assets and business in June.
Smith was then elevated to chairman in May following the departure from the board of Malcolm Murray, a month after Green himself quit as chief executive amid an investigation into his links with former Rangers owner Craig Whyte, although he denied any wrongdoing.
However, the tension and split at the heart of power which was once defined through Murray and Green's fractious relationship continued to simmer under the surface until a group of disgruntled shareholders launched a bid for boardroom power last week.
Green's first act after being appointed as consultant was to conduct a press interview in which he stated McCoist had to win a cup this season, and implied that his successor Craig Mather had been too generous with his player budget.
Hours later, Rangers crashed out of the League Cup at Forfar before McCoist launched a stinging attack on Green, branding him an "embarrassment" and accusing him of having contempt for the club and Scottish football in general.
McCoist today described his mentor Smith as the "glue" that was holding Rangers together and his resignation adds to the huge uncertainty over the direction of the club.