Emma Hayes has said that Chelsea were "robbed" in their Champions League semifinal loss on Saturday, describing the penalty awarded to Barcelona as the "worst refereeing decision in women's Champions League history."

Barça overturned a 1-0 first leg deficit to beat Chelsea 2-0 at Stamford Bridge, however, referee Iuliana Demetrescu's debatable decision to dismiss Kadeisha Buchanan after two yellow cards left the Chelsea boss seething.

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Buchanan was booked in the 54th minute for a clear foul however, the second booking, just five minutes later, was deemed a harsh decision by Hayes who gave a scathing assessment of the officiating.

"I was surprised when I saw her [the referee] selected," Hayes told a media conference after the defeat. "She's known for easy cards and I think that was probably the worst decision in UEFA Women's Champions League history.

"Even Barcelona players said to us the referee was helpful for them. I didn't think it was a foul, let alone a yellow card.

"It's almost like I'm stood there, and I've looked at the fourth official and said, 'Surely that will be checked?' She said she can't, it can't on a yellow.

"When you work so hard over days, weeks, months, years, you come here, and you expect the best from our officials. We expect that at the very least. It is really hard to take."

Chelsea entered the tie 1-0 up from the first leg. Aitana Bonmatí and Fridolina Rolfö netted in the second leg to book Barça's ticket to Bilbao for a fourth consecutive final next month.

The game was Hayes' last at Stamford Bridge before she departs the club at the end of this season after 12 years to become the head coach of the United States women's national team.

The Champions League is the one trophy that has alluded Hayes during her tenure, and she admitted the loss is hard to take.

Hayes also said that the questionable penalty awarded for a challenge on Bonmatí was "equally soft."

"When you get a shocking decision, there's nothing you can do about it. It's hard enough for us when you've got 11, but with 10, it's virtually impossible.

"The toughest thing to take is that we didn't lose it. There's nothing you can do when there's such a terrible decision, and it's already hard enough. We didn't feel we got the opportunity to lose it; that was taken away.

"When that's taken out of your hands, that's the tough one for the players. I'm gutted for them. We were robbed. I genuinely believe we were on top of the game. You need everything to go your way.

"They get two yellow cards, a deflection and a penalty. Everything went their way, and everything didn't go our way tonight."

Ahead of the pivotal decisions in the second half, Hayes believed Chelsea were leading the tie despite lacking clinical finishing in front of goal in the first half. Mayra Ramírez was missing from the lineup after picking up an injury in training the day before the game which Hayes also believed affected the side.

"They had a strong first half, but the deflected goal puts them in a good position.

"In the second half, I felt we were just coming on top, and you could see the combination of the crowd and players were driving us, and the players felt really confident.

"Up until the second yellow, we were on top. I could feel the momentum from the crowd and the players and the official has made a horrific decision. We can't talk about anything else."

Barcelona manager Jonatan Giráldez did not share Hayes' view on the refereeing and insisted that Barcelona were deserving of their victory.

"It's part of the game; when we play at home, we create a penalty and centimetres, two or three centimetres, we were disallowed in that situation, so it's part of the game," he said.

"The most important thing for me is management of the emotions when you are winning and when you are losing the game.

"Today we were better than Chelsea, in the first leg we were better than Chelsea, we create more than them and we deserve the victory."