"Cardiff's cash offer falls well below our valuation of Jason and has been immediately rejected," said Chairman Jeremy Peace.
"Cardiff have yet to meet our asking price and unless they do Jason won't be joining them.
"We are also not interested in loaning Jason back to Cardiff.
"Cardiff have known what offer we would accept for Jason for a year.
"This was made crystal clear when Jason joined them on loan last summer and reconfirmed during talks last month."
This comes on the day that Koumas again failed to turn up for training.