The Hong Kong businessman had been given until Friday to prove he could raise the £35million needed to complete the deal, but the takeover shows no signs of progressing.
"The deadline is 21 December but proof of funds was supposed to be confirmed by Friday and it has not happened.
"I must stress that the fact the deadline that was set by Birmingham has passed does not mean to say that a deal cannot be done still.
"For instance, if Mr Yeung is going to use his own money to buy the club, he could walk into our office on 20 December with a cheque for what is needed and then say 'give me the shares.'
"But if he is going to borrow the money, which I understand is going to be the case, we have got to see some sort of activity two or three weeks ahead of the deadline, otherwise the deal can't be done.
"We want proof of funds. That is what we want to see. That is what they haven't shown us."