The Certification Officer watchdog has ordered Ucatt to conduct a re-run of its 2009 leadership race which saw Ritchie returned as general secretary.
The CO said the election result should be treated as “void and of no effect” and Ritchie “shall cease forthwith to hold office as general secretary.”
A new election will now be held with a result due by the end of July.
The removal of Ritchie follows a determined campaign by his defeated rival in the 2009 election.
Regional official Mick Dooley lost the leadership race by 6,706 votes to 4,431.
But Dooley claimed the election was unfair because less than 50% of Ucatt´s 130,000 members received ballot papers.
The CO judgement shows that Ucatt claimed to have 130,000 members but only sent ballot papers to 56,867.
Certification officer David Cockburn said: “In my judgement the election was so flawed as to be a nullity.”
Since launching his complaint against the election, Dooley has been in constant conflict with the Ucatt leadership and was sacked by the union earlier this year.