Dundee boss Paul Hartley last night backed under-fire referee Willie Collum – and insisted he had no worries about him taking charge of tomorrow night's televised clash with Celtic.

Collum has been in the headlines recently for a string of controversial calls.

The latest flashpoint came during Aberdeen's 2-2 draw with Inverness at Pittodrie at the weekend.

The top-flight whistler was blamed by Dons gaffer Derek McInnes for costing his team the chance to go above leaders Celtic at the top of the table.

McInnes reckoned Collum got it wrong when awarding Inverness a penalty that allowed them to go 2-0 ahead, while counterpart John Hughes was equally adamant Adam Rooney should not have had the chance to level from the spot.

Now Collum is bracing himself for another testing 90 minutes in front of the live cameras as champions Celtic prepare to roll up on Tayside, but Hartley has no concerns going into the midweek showdown.

Hartley said: “I don't think it's a concern. He's a good referee.

“I think referees make decisions at times which don't go down too well.

“By all accounts, there were a few during the Aberdeen game at the weekend although I didn't really see it.

“I just feel we have to get on with it. I think we've got to respect the referees also whatever decisions they make.

“Hopefully he can just referee the game on Wednesday and it's a good game and there's not too many decisions which are bad.

“You've just got to let him referee the game. Obviously the spotlight will be on him.

“But I definitely have sympathy. It's split-second decisions, isn't it?

“Sometimes they make good decisions and bad decisions but it's a tough job they've got.”

Dundee go into Wednesday's clash with Ronny Deila's league leaders on the back of a 5-2 Highland hammering from Ross County.

And former Celtic midfielder Hartley has warned his side they can't afford to switch off the way the did against County when the Hoops arrive on Tayside.

He added: “It's a must. It's something you have to make sure that you're switched on all the time.

“No matter what team they have out with their players and personnel, having been at their game with Hearts on Sunday I thought they started really well.

“And they also started the second-half really well.

“They've got players who can hurt you and a strong squad.

“So we've got to make sure that we're really focused and concentrate for the whole game on Wednesday.

“I just felt that was a freak result against County.

“I didn't see it coming.

“But we do have to make sure we are at our best come Wednesday.

“I think we can cause any team problems.

“That's something we have shown in the majority of games.

“We've got players to do that, and Kane Hemmings is on fire just now while Gregt Stewart is getting better.

“His lead-up play has been good and his decision-making has been good in the last couple of games.

“Gary Harkins has also been coming onto a game in the last couple.

“We feel we can cause them problems with the front players we have.”

Meanwhile, Dundee keeper Scott Bain is expected to be fit after sustaining a shin injury in their weekend defeat.

Hartley said: “Scott's a little bit sore and has a few stitches on the shin.

“But he should be Ok.

“He didn't train today but it shouldn't be a problem.

“He got a sore one but it could have been worse.

“We had a few more not training so we;ll just have to wait and see how they are over the next day or so.”