The vote is a considerable embarrassment to John Edmonds, leader of the GMB general union, who has conducted a high-profile campaign in favour of partnership at the workplace and against macho management.
Mr Edmonds is among a senior group of TUC representatives who regularly visit Downing Street to make representations on behalf of the British workers.
The Independent understands that employees of the GMB, who are also members of the union, have voted by nearly four to one to take industrial action, and a smaller group who belong to the Manufacturing Science Finance union are expected to follow suit.
The results of both ballots are due to be released next week amid what one union source described as a "climate of fear".
In addition to allegations of bullying and intimidation, staff morale has been undermined by a restructuring scheme, which many of them oppose. A substantial proportion of headquarters staff are believed to have registered interest in a severance scheme.
There have also been complaints against senior staff at union offices in the West Midlands.Reuse content