Recognition would have given the union the authority to conduct collective bargaining on behalf of FCA staff.

The CAC rejected Unite’s request on the basis that only 15% of FCA staff were in favour of the move.

The arbitrator said an application is not admissible unless its panel decides that the majority of workers would be likely to favour recognition of the union.

It also expressed some concerns about the veracity of the union’s petition due to duplicates and false entries in the initial online survey results which had been publicly referenced, including reports in the press.

The CAC decision said: “‘Having carefully considered the parties’ submissions, the panel does not consider that the evidence before it is sufficient to enable it to conclude, on the balance of probabilities, that a majority of the workers constituting the proposed bargaining unit would be likely to favour recognition of the union as entitled to conduct collective bargaining on behalf of the bargaining unit.”

Unite had applied to the independent Government-funded arbitrator for formal recognition on 17 December.

The union currently represents around 650 FCA staff.

Last week Unite members at the regulator carried out a 48-hour walkout in protest over pay, terms and lack of trade union recognition. 

The strike is believed to be the first ever industrial action at the regulator.