David Gold speaks out over Karren Brady re-arrest
Mr Gold said the investigation centred on tax and national insurance payments, adding: "It is completely wrong that our managing director has been picked on and singled out.
"For the complete avoidance of doubt, I want to make this 100% clear that, as we stated before, this matter is all about PAYE and NIC on two players from 2002 and 2003, and absolutely nothing has changed.
"The figures alleged to be involved are not substantial and not material to the company.
"The club employs highly-respected accountants and auditors and has always provided them with complete access to their accounts and other financial information.
"The club believe that it would be more appropriate that questions about financial matters be directed to them."
Mr Gold stressed that the club "takes its financial responsibilities seriously".
A City of London Police spokeswoman confirmed last night that a 39-year-old woman was arrested as part of the continuing football investigation.
She said it was not possible to provide details of the alleged offence, adding: "We have been working with HM Revenue and Customs (HMRC) from the outset of the investigation.
"The investigation has always focused on money laundering.
"The Fraud Prosecution Service has identified that tax offences may be involved."
Birmingham City later released a statement stressing that Ms Brady had not been charged by police and "vehemently" denied any wrongdoing.
The statement said: "In the fullness of time, we believe the public will see that no offence has been committed by anyone at BCFC.
"The club continues to assist the police with their inquiries and have answered every question put to them."
In November 2007, officers arrested a series of high-profile figures in the national game in a controversial series of raids.
Other figures who remain on bail are believed to include former Portsmouth boss Harry Redknapp, the club's chief executive Peter Storrie, former chairman Milan Mandaric, former player Amdy Faye and agent Willie McKay.
Ms Brady became the UK's youngest football managing director when Birmingham City floated on the stock market in 1997.
She is also chairman of Kerrang! magazine and non-executive director of Channel 4, Mothercare and Sport England.
The HMRC said it was not making any comment.
