Willie Collum has apologised to Roma for the blatant blunder which cost the Italians a Europa League victory against Borussia Monchengladbach.

The Scottish referee inexplicably pointed to the penalty spot in injury time at the Stadio Olimpico after Chris Smalling was clearly struck in the face by a shot. 

Collum was adamant it hit the arm of the on-loan Manchester United man and, despite disbelieving protests, the decision stood and Lars Stindl stepped up to secure a 1-1 draw.

Roma superstars including Smalling, Edin Dzeko and boss Paulo Fonseca lined up to lambast the whistler after the fixture. 

However, the official Twitter account of the Serie A giants revealed that Collum was contrite following the incident, claiming that he formally apologised for his error.  

They wrote: “ASRoma’s management spoke to the match officials after the game and they admitted that the decision to award the penalty was a mistake. 

“We respect and thank them for their genuine honesty and now we focus on the next game.”

Roma were leading 1-0 at the time of the incident thanks to a strike from Italy international Nicolo Zaniolo and were on course to hold firm and take full control of their Europa League group. 

Smalling tweeted after the match: “Disbelief that this decision went against us...We deserved the 3 points, so disappointed…”

Fonseca added: "It's hard to accept a decision like that. All my players feel devastated.”

Roma do remain top of Group J after the controversial draw, but in a far less enviable position. 

They are just one point ahead of Istanbul Basaksehir and Wolfsberger in a section which remains in the balance. 

Speaking to the Italian media in the immediate aftermath of Collum’s call, former Manchester City front-man Dzeko revealed that the referee ignored his pleas to reconsider his decision based on the visible evidence on Smalling’s face. 

The Bosnian rued: “I don’t understand how the referee was so sure it was a handball, there’s no way, it’s incredible.

“We could all tell right away. I told him just to look at Smalling’s face which had a mark on it.

“But the referee was so sure, he kept saying it was a penalty."