Celtic boss Ronny Deila pointed the finger at official Alan Muir for missing a controversial penalty incident in his side's 3-2 William Hill Scottish Cup semi-final defeat to Inverness which ended hopes of a treble.

To most inside Hampden Park apart from referee Steven McLean and his additional assistant Muir, stationed behind the goal, it looked clear that Caley Thistle defender Josh Meekings had used an arm to prevent a Leigh Griffiths header going into the net just a yard out.

A scored penalty seconds before the break would have added to Virgil van Dijk's opener for the Parkhead men and with the Highlanders probably reduced to 10 men, the Hoops manager claimed the game would have "finished" with his side looking forward to the final against Falkirk on May 30.

But the match then further turned against the Scottish League Cup winners early in the second-half when keeper Craig Gordon was sent off for tripping Inverness striker Marley Watkins to concede a penalty, which Greg Tansey scored past replacement keeper Lukasz Zaluska.

Inverness striker Edward Ofere's low drive in the 96th minute was cancelled out by Celtic substitute John Guidetti's free-kick but with four minutes remaining full-back David Raven grabbed the winner for the Highlanders.

Afterwards the Celtic boss reacted to questions about the game's biggest incident.

He said: "I don't think I have to say much about that. I think everybody saw what happened.

"Maybe we need seven referees? One on each post.

"Their one task is to look at what is happening in the six-yard box and on the goal line. You can't blame the main referee for that.

"Referees make mistakes as well but this mistake was very hard to take.

"It's a hard blow for the boys and for us. We're very disappointed and we had control 11 versus 11 and we should have killed the game off."

Deila had no complaints about Gordon's dismissal as he added: "That was okay. The rule is as it is. I think the rule is very hard, but that's nothing to do with the ref.

"The other decision is quite different.

"It was a very difficult situation. A 50-50 challenge and he came out a little too late."

While hopes of a clean sweep are over, Deila is looking for the Scottish Premiership leaders to keep on course for the title against Dundee at Dens Park on Wednesday night.

The former Stromsgodset boss said: "It's a tough world and that's why it's so hard to get a treble.

"It's small details that can make you fail and today it was a small detail that made it hard for us.

"We have to get that behind us as quickly as possible and focus on Wednesday

"Good teams bounce back quickly.

"Everybody is very disappointed today, but I've had disappointing moments before in football.

"It's how you handle it and what you learn from it before you move on that's important."