The managing director of Rolls Royce in Bristol has said there is "no basis on which (sacked union official) Jerry Hicks could be reinstated".
Mr Wood said there had been a 'breakdown in trust'
Tony Wood was speaking on the day 96 staff at the Patchway plant went on strike in support of Mr Hicks.
He was dismissed after allegations of misconduct but an employment tribunal provisionally found he had "probably been dismissed on trade union grounds".
The union Amicus has called for the full reinstatement of Mr Hicks.
But Tony Wood said: "There's already been an irretrievable breakdown in the trust between Jerry Hicks and the company both as an employee and in his important role as a trade union representative on the site."
The company said Mr Hicks had been sacked for organising unlawful industrial action earlier in the summer and attempting to undermine disciplinary procedures - claims he denied.
His case is due to appear before a full hearing within six months.
Tuesday's industrial action by test facility engineers could continue for an indefinite period, the union Amicus said.
A supportive rally was due to take place on Thursday, 25 August at the Moorways Sports Stadium in Derby.