Durkin came under fire after admitting Shearer should have had a penalty when he was tripped by United keeper Tim Howard, but sticking by a later decision to disallow a strike by United defender Mikael Silvestre.
"I've seen it again and I've listened to Paul Durkin and I don't agree with him," Ferguson told Sky Sports.
"I think it was a perfectly good goal, as I thought it was a penalty kick."
Shearer was equally forthright, saying: "I should have had a penalty.
"I know if I was playing in red, that would have been a certain penalty, but I suppose it's asking too much for Alan Shearer to get a penalty at Old Trafford in front of the Stretford End."
Relating a conversation over the incident with Durkin, Shearer added: "He said he wasn't 100 percent certain, so I said 'why didn't you book me for diving?' and
Newcastle boss Bobby Robson was more conciliatory over Durkin's admission, saying: "He's been honest and that's as good as it gets. I applaud him for that."
But he added: "It was a big blow for us because it looked as though Howard did catch Alan after Alan was trying to take the ball around him."
As for the draw, which took the champions a point clear of Arsenal at the top of the Premier League, Ferguson said: "We had the better chances, the better spells of pressure but Newcastle put a lot in their game.
"In the first half particularly they pressed the ball everywhere...and I thought we were a bit lackadaisical.
"Second half, we were more ourselves, we speeded up the play and created some good opportunities."
On the injury front, Ferguson said Wales winger Ryan Giggs had pulled a muscle in his lower back and would probably miss next Saturday's game at Wolverhampton Wanderers.
