Phil Parkinson has resigned as manager of Championship new boys Colchester after leading them to promotion in May.
Parkinson has been in charge at Layer Road since 2003
He has been linked with several jobs including the current vacancy at Hull, following Peter Taylor's departure.
Parkinson has another year to run on his contract at Layer Road and the U's have refused to accept his resignation.
The club said: "We have asked him to reflect upon the position and to discuss matters with us further on his return from holiday in a week's time."
"Should we be unable to stop him from resigning the board will do whatever is necessary to protect the club," they added.
The statement continued: "The club will make no further comment at this time until the manager and the chairman, who is also currently on holiday, return."
Charlton, Ipswich and Derby were all denied permission to talk to Parkinson, who guided Colchester to second place in League One on a tight budget.