Sir David Murray insists he was under no outside pressure to relinquish the chairmanship of Rangers.
Murray, who bought the Ibrox club for £6m in November 1988, announced today that he is to step down as a board director and chairman.
He will be succeeded as chairman by Alastair Johnston, 61, a director of the club for the last five years.
It is well known that Murray has been looking to sell Rangers, whose debt is reported to be around £25million, and today's announcement will fuel speculation that the move could be to facilitate an impending buy-out.
However, Murray said the decision to remove himself from the firing line is his alone.
"I know that there will be conspiracy theories but there was no pressure from outside sources to step down,'' he said. "All the the pressure came from myself.
"The club is in a good position and the balance sheet is okay.
"After 20 years it was time to step down and it is a good time to go, there are no outside factors.''
In a statement announced to the stock exchange, Murray said: "As things stand, I remain the majority shareholder at the club and will always have the best interests of Rangers at heart, but it is time to pass on the chairman's baton.
"For me personally, it has been a tremendous honour and privilege to serve as chairman of Rangers.
"There have been so many great moments to savour and it is particularly gratifying to step down when the club are reigning SPL champions, Scottish Cup holders and about to embark on another exciting journey in the UEFA Champions League.
"The club has the governance and management in place, both in footballing and business terms, to deliver further success in the future and Rangers can go forward with confidence.
"I would also like to salute the countless Rangers fans around the world who have shown unwavering support for the club, week in week out.
"They are the lifeblood of Rangers and many clubs would dearly like to have such a great support.
"I am delighted that Alastair Johnston has accepted the chairmanship.
"He is an internationally renowned and respected businessman and will be an excellent servant to the club.''
Following Murray's announcement, the Ibrox board said it was considering proposals to formally recognise his outstanding contribution to Rangers.
Glasgow-born Johnston is a graduate of the University of Strathclyde and vice-chairman and member of the board of directors of IMG, the leading international sports and entertainment group.
He is a lifelong Rangers fan and became a director in February 2004.
He said: "David richly deserves his place in the Rangers history as one of the club's greatest chairmen and his passion has burned brightly for 20 years.
"He invested heavily in the club but has also demonstrated enormous personal commitment at all times.
"On behalf of all Rangers supporters I wish him the very best for the future.
"I consider it a great honour to be appointed chairman of the club and can say to our supporters that the board, management and staff will spare no effort in striving to ensure that Rangers Football Club enjoys a successful future.''
The Rangers Supporters Assembly paid tribute to Murray's period as chairman.
Andy Kerr, president of the umbrella organisation that represents Rangers supporters groups around the world, said: "Rangers fans all over the world will be united today in paying tribute to the passion and commitment Sir David has shown for Rangers over the past 20 years.
"Only 10 days ago, he was given a resounding cheer when he unfurled the league flag at Ibrox and that's how Rangers fans would like to remember what has been, overall, a very successful chairmanship.
"Of course, football fans will from time to time see things differently from the men in the boardroom, that's all part and parcel of the game.
"There has been many a debate among fans over the years about Sir David's contribution to the club but the facts show it was a hugely successful period in terms of trophies and the quality of players we were privileged to see.
"We begin another chapter now under Alastair Johnston's chairmanship and we look forward to continued success for our great club.''