The claim, by former chief executive Mary Allen, will prove acutely embarrassing to Sir Colin, who is also chairman of EMI. The deputy chairman of the Royal Opera House board is a woman, Vivien Duffield, the philanthropist who has given millions of pounds of her own money to the ROH.
She was appointed deputy chairman by Chris Smith, the Secretary of State for Culture, Media and Sport, not by Sir Colin. Relations between Sir Colin and Mrs Duffield are said by insiders to be strained and Mrs Duffield is reported to have threatened to withdraw her financial support from the opera house if the situation does not improve.
Today she is expected to announce a large donation to a non-operatic area; several million pounds to museums.
Mrs Allen, who was chief executive of the opera house until her resignation earlier this year, makes her accusation about Sir Colin in her diaries, which are to be published next month. In a section that has not been serialised and will provoke fresh controversy, she writes:
"He [Sir Colin] then began talking about prospective board members, and mentioned a number of people, all of whom were men. I said that in my experience, groups of this kind functioned better when there are roughly equal numbers of men and women.
"`It's almost impossible to find women for non-executive positions: they're not tough enough,' he replied.
"I told him that I knew a number of very tough women and, if he would find it helpful, I could give him a list of names.
"`No, women can't be tough without being emotional,' he said. I roared with laughter. `That's rich coming from a man.' I said. `Most of the emotion I have encountered at meetings comes from men.'
"`Ah, yes, but that's because we have bigger hearts.'
In another passage Mrs Allen writes: "The discussion then turned to a letter Colin had received from the Arts Council saying, among other things, that they were looking for a gender balance on the Board.
"He then made a number of trenchant comments about Kathryn McDowell [Arts Council music officer].
"He said, quite adamantly, that he didn't know any women who he thought were good enough to serve on the Board."
In one of her entries, Mrs Allen records how she started speaking at a meeting on planning and Sir Colin got up and started offering everyone tea and coffee. he then said: "Oh, go on, unlike most women I can concentrate on more than one thing at a time."