Collingwood had been in the role only a year and had seemingly offered some stability to an organisation which had struggled to maintain a settled team.
As recently as March she told the Guardian she had taken the job as it was "a once-in-a-lifetime opportunity to channel and combine everything I have learnt as an individual and humanist member of society". She added: "Bringing about lasting change in a key social issue like this is an unparalleled challenge, and one I care deeply about."
Derek Lewis, who was appointed as the Trust's chairman in January, has taken over Collingwood's responsibilities as an interim measure, said a WSTA spokesman . He added: "It's important for the industry that the Trust works. Lewis is looking to ensure that the Trust continues the good work it is doing."