Trading in club shares was suspended yesterday morning after it emerged Brady, 39, and Sullivan, 59, were questioned by officers from City of London Police’s economic crime unit.

The club’s offices were raided by the same unit last month.

And at his pre-match press conference ahead of the crucial Barclays Premier League clash with Everton tomorrow, McLeish said: “It has not been that unusual over the last year or so. I think we have seen other incidents, shall we say.

“It seems to be part of football life at the moment.”

He added: “I am sure Karren and David will be okay out of this.”

Detectives confirmed they arrested a 59-year-old man and a 39-year-old woman on suspicion of conspiracy to defraud and false accounting, but refused to comment on exactly where and when the arrests were made.

The pair were released on bail, police confirmed.

A statement from City of London Police said the arrests were made “as part of the City of London Police’s ongoing investigation into football corruption”.

As trading resumed at 2pm yesterday Mr Sullivan said he was “shocked” and branded the police statement “very unfair”.

Speaking from his office at home in Theydon Bois in Essex, he said: “I’m shocked by the whole thing.

“The police statement was very unfair.

“It is to do with two foreign players and the PAYE on those players. This is a complicated tax matter.

“We answered every single question they put to us. We have absolutely nothing to hide. We have done nothing wrong, and we think in due course this will be proven.”

In an official statement released yesterday, the club said: “The City of London Police investigation is focusing on payments to a football agent and two players dating back to 2002/2003.

“There is absolutely no allegation that any director of the company or the club itself has benefited financially from any of this activity.”

The statement, released to “clarify the situation”, continued: “Insofar as there may be any implications for the company, these are not considered material to its financial affairs and they are in relation to the payment, or possible non-payment, of PAYE and National Insurance contributions.

“The club and its directors are co-operating fully with the police in this investigation and will continue to do so.

“For the avoidance of doubt we wish to make it plain that David, Karren and Birmingham City FC deny absolutely any wrongdoing.”

Brady and Sullivan had been interviewed by police “by long-standing appointment” on Wednesday, a club spokesman said.

He added: “For the avoidance of doubt, no charges have been brought.”

Ms Brady became the UK’s youngest managing director when Birmingham City floated on the stock market in 1997.

She is also non-executive director of Channel 4 and Sport England.

Leaving her home in Knowle, Solihull, for work yesterday, she made no comment.

Mr Sullivan, the multi-millionaire former proprietor of the Daily Sport and Sunday Sport, co-owns Birmingham City with brothers David and Ralph Gold.

Detectives investigating alleged corruption in English football made seven arrests as part of the same inquiry last November.