Craig Brown has quit as Motherwell manager little over 24 hours after pledging his continued allegiance to the club following an approach from Aberdeen.
Motherwell confirmed the resignation of Brown and assistant Archie Knox after they reopened talks with Aberdeen chairman Stewart Milne.
Brown is now set to be named Aberdeen manager in time for the Dons' Clydesdale Bank Premier League clash against Hearts on Saturday.
A strongly-worded statement by Motherwell read: "We are surprised and disappointed by the decision of our management team to leave the club at this time and in this way. But it is not in our ethos as a club to stand in anyone's way that wanted to be somewhere else.
"We also have far too much respect for Craig and Archie and what they have achieved in the game to do anything other than wish them happiness in what they are setting out to do and to thank them for their efforts in the last year. It is very difficult to understand their decision but we must respect it.
"Separately we do wish to make clear that as a Board we believe that the conduct of the board of Aberdeen in this matter has been wholly inappropriate and in clear breach of SPL rules as well as basic courtesy. At no point did they inform us or seek our permission to speak to critical employees of our club and to seek to entice them to leave our employment."