The chief executive of the National Trust for Scotland Mark Adderley resigned last month, a move that insiders said was down to a difference of opinion with the board about the trust's direction. His resignation follows a period of financial difficulty for the National Trust for Scotland, which had a deficit of £0.8m at the time of his exit.

Alan Denney, national secretary of union Prospect, said: "We have a period of uncertainty again. There is no chief executive and there is uncertainty about the future. That will have an impact on morale."

A spokeswoman for the National Trust for Scotland said they had begun looking for a replacement for Adderley, but there was no timescale, as the priority was finding the right person.