Ronny Deila insists the penalty claim which went in Celtic's favour in the 3-0 Scottish Premiership win over Dundee United cannot stand comparison with the one that got away last week.

The third goal in Leigh Griffiths' second-half hat-trick at Tannadice came courtesy of a spot-kick awarded six minutes from time, but television pictures showed that United skipper John Rankin's initial contact on Hoops' substitute Gary Mackay-Steven came outside the box.

The irony was not lost on those who had witnessed another traumatic week in Scottish football following referee Steven McLean's refusal to award the Scottish Premiership leaders a blatant penalty for a Josh Meekings handball in the 3-2 William Hill Scottish Cup semi-final defeat by Inverness last Sunday.

Celtic wrote to the Scottish Football Association seeking an explanation and Meekings was offered a one-game ban by the SFA's compliance officer Tony McGlennan before the case was dismissed, leaving him free to play against Falkirk in the final.

The Hoops re-established their eight-point lead over Aberdeen at the top of the table with Sunday's victory but Deila appeared to be still sore about the way his dreams of a treble were ended against the Highlanders and would not broker comparisons between the two penalty decisions.

The Norwegian said: "I agree (decisions even up over a season) but what happened last Sunday was not normal.

"This is a totally different thing. I rarely talk about referees' decisions but last Sunday was a thing that really affected the game.

"We had full control over the game, we were 1-0 up and we had assistants on the goal-line also so I don't think you can say that this was the same as what happened today.

"It was a totally different thing. And the cup of course, is one game, so it is different.

"If it was wrong today it would not have affected the game.

"If it was only 1-0 I could understand it could be an issue. I don't mind if we win 2-0 or 3-0, we deserved to win the game."

Celtic will clinch the title if they beat Dundee on Friday night and Aberdeen do not beat Dundee United on Saturday.

Deila said: "We have to beat Dundee on Friday and that is what we are aiming for.

"I want to win (the title) as quickly as possible."

Griffiths insisted the Parkhead club were due a bit of luck after their Hampden disappointment.

He was also grateful that nominated penalty taker Kris Commons gave him his chance to take his tally up to 18 and to become the club's top scorer.

He said: "I heard it was outside the box but we were due a bit of luck after the semi-final last week so I will take it and take the match ball too.

"Kris Commons is the normal penalty taker but I said to him I was on my hat-trick so he handed me the ball.

"He is good like that. He did it with Anthony Stokes earlier in the season so I am happy he gave me it."

Dundee United boss Jackie McNamara was prepared to cut referee William Collum and his assistants some slack.

He said: "Like everybody else - well, maybe not everybody else - I thought it was out of the box.

"The referee has made a mistake but that happens, as we have seen over the piece.

"It doesn't matter we were losing 2-0, it is still a goal conceded and it does matter but it is a mistake, the same as the players made mistakes for the first and second goals. It happens, officials are human."