Bayern Munich has been alerted following Champions League referee call

The German club says it will support a formal complaint against the official

Bayern Munich has been alerted following a controversial Champions League refereeing decision that has sparked a formal complaint from the German club.

The incident occurred during Bayern's 2-1 defeat to Barcelona in the first leg of their semi-final clash at the Camp Nou on Wednesday night.

With the game poised at 1-1, Bayern were awarded a penalty after Barcelona defender Javier Mascherano brought down Robert Lewandowski in the area.

However, referee Viktor Kassai reversed his decision after consulting with the video assistant referee (VAR), much to the fury of Bayern players and officials.

Bayern sporting director Hasan Salihamidzic has since confirmed that the club will support a formal complaint against Kassai, who he accused of "lacking character".

"We will support a formal complaint against the referee," Salihamidzic told reporters.

"He lacked character. He made a decision and then changed it. That's not possible."

The decision has also been met with criticism from UEFA, with president Aleksander Ceferin saying that he was "not happy" with the way it was handled.

"I'm not happy with the way the VAR was used last night," Ceferin said.

"We need to make sure that the VAR is used in a way that is fair and consistent."

The second leg of the semi-final tie will be played at the Allianz Arena on Tuesday night.

Bayern will be looking to overturn the 2-1 deficit and reach their third Champions League final in four years.