Mr Salsbury, who is 49 and has worked at M&S since joining as a management trainee 28 years ago, will move up to the top job in January when current chairman and chief executive Sir Richard Greenbury takes a step back to become non-executive chairman. Sir Richard will retire in May 2000, a year earlier than anticipated.
The re-shuffle leaves no place for Keith Oates, the deputy chairman who made a high-profile, last-ditch challenge for the job this month. He leaves with immediate effect with a pay-off yet to be finalised. He said he was "disappointed" at the board's decision but that he looked forward to "one more full -time role" either in the UK or overseas.
The succession marks a victory for the combative Sir Richard who has made no secret that Mr Salsbury was his favoured heir. But the new boardroom structure received a mixed reaction from City analysts with some saying the company required more radical change.
As the shares fell 24.5p to 421p, one analyst said: "It is disappointing. It is a victory for the old guard. Oates was the only guy who stood up to Greenbury and he's been kicked out. Salsbury has presided over the worst clothing season M&S has ever had."
Others were more charitable and said that Mr Salsbury may prove more innovative than he has been given credit for.
Yesterday the usually secretive M&S appeared to usher in an era of glasnost with a more open approach to the City and the press.
Looking relaxed, Mr Salsbury said he was "delighted" with his elevation and pledged to modernise the company, which has become overly bureaucratic and centralised.
"I am really keyed up. This is a tremendous and exciting opportunity. Anyone who walks into a job like this and says they do not feel a sense of change would be lying."
Mr Salsbury said he would look at the size of the company's board, which with 21 members is seen as unwieldy. He also wants to streamline decision making and devolve responsibility.