In a statement Mr Cowper, now aged 71, said: “The last ten months have been very difficult for me with acrimonious relations developing within the council. This latest situation started to affect my sleep patterns seriously and my health began to suffer.
“I want to maintain an active lifestyle as long as I can and this situation wasn’t doing me any good at all.
“I have carer responsibilities for my dear mum, who will be 102 soon, and I accept them gladly.
“If you are in that situation yourself you will know you need to be fit and healthy yourself to deliver the proper level of care and quality of life to another person.”
His swift fall from grace coincided with a governance review of the council carried out by independent inspector David Bowles last year.
The council says the review report will be released in December.
In March, Grayshott’s district councillor for 21 years was stripped of the role as portfolio holder for Whitehill and Bordon and removed from the council’s ruling cabinet.
Mr Cowper was twice council leader, from May 2006 to October 2009 and from May 2013 to 2017.
In 2009, Cllr Cowper launched the widely-praised Bordon regeneration project.
It finally got going properly after the army began leaving the town in 2011, with the last elements going in 2014.
In announcing Cllr Cowper’s resignation in an email sent to district councillors just minutes before 5pm last Monday, the council was devoid of praise or acknowledgement for his work.
And in a statement, council chief executive officer Gill Kneller said: “Cllr Ferris Cowper has resigned as a member of the council. This means that there is a councillor vacancy for the Grayshott ward.
“We can’t consider a request for a by-election at this stage because of the coronavirus pandemic.”