The referee who earned the wrath of Aberdeen boss Derek McInnes last week has received an official complaint about another poor display.

Fuming McInnes claimed Bulgaria official Nikola Popov was “out of his depth” as they lost 1-0 to Maribor in Slovenia to go down 2-1 on aggregate in their third-round Europa League qualifier last week.

But Bulgarian FA chiefs are now investigating a complaint made by Levski Sofia after he made a string of poor decisions against them in a 2-2 draw with Lokomotiv Plovdiv on Sunday.