Macdougall, who headed up Arthritis Care's South East England region, has since joined healthcare charity Ataxia UK as chief executive.
He left Arthritis Care on 12 March after 10 years, in the wake of a radical reshaping of the charity's structure.
The trustee board and chief executive Terry Oliver has said the restructure is needed to better manage the charity's finances, create a more professional organisation that lobbies at a political level for all people with arthritis, and protect trustees from litigation.
But many members have been outraged by the changes and by the lack of consultation before the new structure was announced. Much of this indignation has been vented on a website of Arthritis Care's grass-roots supporters, and in mid-April Macdougall added his comments.
"Arthritis Care's trustees and chief executive will have you believe that the regional directors in England accepted voluntary redundancy and left of their own volition. This is not true," he said.
He claimed that all four regional directors were offered "demoted posts" or were invited to apply for the role of director of England, "a post that was generally agreed to be undoable".
"The view of Acas mediation service was that we were being made compulsorily redundant."
He added that although Arthritis Care did not contravene employment law, "the morality of their action was certainly questioned". He said his last day passed without any acknowledgement from the chief executive or chairman that he was leaving.
Macdougall admitted that change is needed within the charity but objected to it being imposed "by bureaucratic decree".
However, he also added that the charity's members must "start thinking about how best to address the needs of all people with arthritis and not just a minority membership".
The charity said it "deeply appreciated" Macdougall's efforts and hard work and was sorry this was not conveyed to him when he left. It said it would be inappropriate to comment further on his remarks, but added that it was only fair to recognise Arthritis Care's successes to date in persuading the Government to treat arthritis as a health priority.
The charity's trustees are meeting the chairs of the charity's area committees on 6 May in a bid to head off the vote of no confidence which has been mooted for the AGM on 8 July.