Birmingham accused Aston Villa of trying to "tap up" its former manager after the crosstown rival said on Tuesday it will interview Alex McLeish about its vacant coaching position.
Birmingham issued a statement saying it will lodge a formal complaint against Villa for what it called "a contempt of Premier League and FA rules" and said Villa's behavior could "set a very bad precedent."
Fans of both clubs have expressed outrage this week over the prospect of McLeish taking over Villa after he quit the newly relegated Birmingham on Sunday.
Villa said earlier on Tuesday, that it believes McLeish is a free agent after resigning, but Birmingham said it will try to prevent any talks between the two sides.
"The club feel this will taint football and give the game and the footballing authorities a bad name if this is allowed to materialize," Birmingham said in its strongly worded statement. "The club will do what is within its powers to prevent this and will lodge a formal complaint to the authorities tomorrow (Wednesday) as there is now not the slightest doubt remaining about this tap up attempt."
Villa is searching for a replacement for Gerard Houllier, who left last week because of heart problems after just nine months in charge. Former Fulham manager Mark Hughes has also been linked with the post, and Birmingham stressed that even Villa's own fans are against hiring McLeish.
"This is also an attack against the intelligence and integrity of not only the Villa fans, but most importantly our fans who are badly let down after having just been relegated," the club said. "It is definitely a bitter pill to swallow for all fans concerned, both here and across the city. Never have the two clubs seen such a strong unity between their rival fans and this unity is based on humility and integrity and what is right and fair."
Villa's statement earlier Tuesday was meant to ease concerns among its own fans, but stressed that McLeish's tenure at Birmingham should not disqualify him from the job.
However, it said the club board has taken "the strong emotions associated with this very seriously."