The Enquirer understands that Ritchie quit his current role and handed in his union membership yesterday.
The dramatic move is the latest twist in a turbulent 12 months for Ritchie.
He was removed from office last year following the discovery of voting irregularities.
Ritchie was installed as an office administrator in Glasgow on full pay following his demotion.
He was facing an internal investigation into alleged expenses irregularities but collapsed at the latest hearing last week.
One union source said: “The whole situation has become a joke but this latest move was a bit of a surprise.
“It seems incredible that Ritchie was stripped of office but then put on full pay while an investigation was carried out which now has been stopped in its tracks by his resignation.”
A UCATT spokesperson said: “Alan Ritchie has resigned from his employment and from the union”.