Gary Hooper’s close-range strike after 23 minutes gave Neil Lennon’s side the interval lead and second-half goals from Beram Kayal, Kris Commons and substitute Daryl Murphy, on for Scott Brown, sealed the win.
It was a convincing performance from the home side, who could go top of the table on Wednesday when they travel to Inverness for their game in hand over the Ibrox men.
However, a routine win had a sting in the tail after Dundee Utd manager Peter Houston said he would seek “clarification” from the Scottish FA’s head of referee development, John Fleming, after claiming that referee Iain Brines told him that “on another day” he would have booked Celtic midfielder Beram Kayal for a foul on Craig Conway.
In the first-half of Celtic’s 4-1 win at Parkhead, Brines had a word with Kayal after awarding a free-kick for his tackle on the Tannadice midfielder as he raced down left. Houston was raging that a similar challenge by Jon Daly on Charlie Mulgrew in the closing stages of the game led to a yellow card for the United substitute.
The United boss said: “The one thing I want to mention is that I’m disappointed with the referee. I don’t want players sent off or yellow-carded, it’s not my style but to me, Kayal taking Conway out was a stonewall yellow card.
“Seconds left in the game and Jon Daly, in my opinion, does the exact same thing to Charlie Mulgrew, catches him a second too late. I hold my hands up, we were beaten fair and square but what annoys me is that I asked the referee for an explanation in the tunnel and his explanation was that on another day the Conway one would have been a booking.
“What’s that about? What does that mean? It baffles me. I need to speak to John Fleming because it’s bugging me.
“I want clarification on what days you get a yellow card for that and which days you don’t. Simple as that.
“He said it in front of his assistants and a couple of police were there as well and I said he would need to explain it to me.
“He started walking away saying ‘that’s enough’ as I was ranting. What are we going to decide, ‘it’s a sunny day today so I’m not going to yellow card him’?” Celtic boss Neil Lennon had a different take on Kayal, who scored the goal of the game with a strike from outside the box.
“I thought he was world class,” said Lennon. “I thought he and Scott Brown were magnificent from start to finish and had to cope with three in there. We wanted to play with a bit of width today with James Forrest and Kris Commons and those two had to really work hard and the strength and power they bring to the team is fantastic.”
CELTIC: Forster, Wilson, Izaguirre, Majstorovic, Mulgrew, Forrest (Ki 64), Brown (Murphy 86), Kayal, Commons, Hooper (Maloney 75), Stokes.
DUNDEE UTD: Pernis, Dillon, Kenneth, Severin, Dixon, Scott Robertson, Buaben (Russell 57), Gomis, Conway, Swanson (Daly 56), Goodwillie.
Referee: I Brines (Scotland).