A quick Google search of this appears to suggest it was a comment made to a reporter in the evening times in 1998?
Google also showed this on an old thread here on FF:
Daily Record (Glasgow, Scotland); 11/7/1998; McILWRAITH, GORDON
JOCK Stein and the Celtic board covered up allegations made against Boys' Club founder Jim Torbett,
Mr Birt said: "There was a lot of hearsay and it wasn't until Jim came back that I got involved because things started up again."
He told how he took the allegations against Torbett to the Celtic board and Stein and even told the then vice-chairman, Kevin Kelly, about them at a meeting in his car.
He said: "Although there were people who spoke to me I couldn't go to the police without actual proof of the allegations. When I joined as chairman, I was told by Jock Stein to keep the name of Celtic Football Club clean at all times."
Billy McNeil said, on oath in a court of law, "It was an open secret at Parkhead"
Unsure if this is in any relation to what anyone needs. Will edit/remove if unnecessary.