Ridsdale said in the statement to the Stock Exchange: "After five years as chairman I have decided to step down and hand over the reins as chairman to Professor John McKenzie who has my full support."
"This has been a very tough six months for the company and our performance both on and off the pitch has been unsatisfactory.
"This means that tough action has had to be taken to generate funds from player sales and to reduce costs both on and off the pitch. Although difficult, it is necessary to balance our books to suit our current position."
Ridsdale was re-elected just four months ago on the summise that he would bring stability to the club. However, despite more sales of top players the debts have climbed to £78.9m in the six months ending 31st December, according to results released to the Stock Exchange.
That figure does not include what it will cost the club to pay-off former manager Terry Venables, who was sacked after just eight months in charge, and his annual contract was worth an estimated £2million.
