Ucatt general secretary Alan Ritchie has been ordered to step down from his post after a union watchdog declared his election void.
The Certification Office for Trade Unions told Ucatt it must re-run its 2009 leadership race after defeated candidate Mick Dooley led a concerted campaign to challenge the result.
In a written statement to Mr Dooley, COTU certification officer David Cockburn said the election should be treated as “void and of no effect”.
It said: “The person elected in that election, Mr Ritchie, shall cease forthwith to hold office as general secretary.
“The union shall conduct a further election for the position of General Secretary to be conducted in accordance with the rules of the Union. It shall be conducted so that its result is declared no later than Friday 29 July.”
Regional official Mr Dooley claimed the election was unfair because less than half the union’s members received ballot papers to vote.