Brondby coach Thomas Frank has quit the Danish top-flight club after being criticised by the chairman on an online fan forum, while the chief executive has been sacked.

Frank’s departure came after it was reported that Brondby’s major shareholder, Jan Bech Andersen, had criticised him on the fan forum SydSiden Online under a pseudonym using his son’s account.

“As of today, head coach Thomas Frank has resigned from his position,” Brøndby wrote. “We are working to find a temporary head coach for Brøndby IF’s Superliga team.”

Andersen, who owns more than 25% of the club, has since acknowledged he was behind the criticism on the fan forum and has apologised.

“It is no secret that the relationship between Jan and me has been strained from time to time, and after the last days of massive media attention, he and I had a talk,” Frank told a press conference on Wednesday. “Based on that talk, I have chosen to end the cooperation.”

Frank, 42, had been the head coach of the club since 2013 following stints as the coach of Denmark’s under-19 and under-17 national teams.

Brondby also announced they had fired their chief executive Soren Vadmand shortly before posting a loss of 17m Danish Krone (£1.75m) for 2015. The chief financial officer Jesper Jorgensen will take over and become the eighth CEO in as many years.

Brondby are fifth in the Danish championship, 10 points behind the leaders FC Copenhagen.