|The AA has more than three million personal roadside assistance members|
family of its former executive chairman - sacked earlier on Tuesday for "gross misconduct".
In a statement to the City the motoring services group said Bob MacKenzie had left the company with immediate effect though it refused to explain why, except to say it was a "personal conduct-related matter".
The Times later quoted a relative as saying the 64-year old had actually resigned on Tuesday morning and been admitted to hospital with an "extremely distressing mental health issue."
Peter MacKenzie, one of his three sons, added that his father was "very unwell" and reportedly requested the company "act responsibly towards a loyal servant."
Bob MacKenzie led a management buyout of the AA and its flotation in 2014. Pic: AA
The AA had no further comment to make when approached by Sky News to respond to the remarks.
It had also earlier declined to comment on whether Mr MacKenzie's departure was linked to alleged activity at the company.
But it did confirm there was no connection between the sacking and a separate warning of a hit to annual profit expectations.
Shares tumbled 18% when it reported that "significant spikes in demand" in June and July meant it had not had enough roadside patrols in place to help drivers.
The AA also pointed to a negative impact from two other issues including an earlier-than-expected bill related to a profit-sharing arrangement.
It said the cumulative effect of the costs would mean its full-year performance expectations falling in line with those of the previous financial year, when trading profits stood at £403m.
Analysts had expected to see trading profits of around £413m in 2017/18 - the first growth under a group transformation plan.
Stock in the FTSE 250 firm closed 14% lower.
The AA had previously announced that the group was to split the executive chairman role as part of efforts to ensure best practice in corporate governance after he led the company to its flotation in June 2014.
He will be succeeded by non-executive chairman John Leach while fellow AA director Simon Breakwell, the founder of Expedia, was named acting chief executive.