Around 3,600 UAW workers at five American Axle plants in Michigan and New York left their jobs in February to protest the company's plans for deep wage and benefit reductions from its union workforce.

The resulting parts shortage has hit 29 GM factories and over 39,000 workers.

The latest development in the conflict has come out of the union's refusal to bring a federal mediator to the table, as requested by American Axle.

UAW president Ron Gettlefinger issued a statement, saying: “While the UAW had conversations with a representative of the Federal Mediation and Conciliation Service, it was concluded that a mediator could add little to the process at this juncture; in fact, it would place the mediator in a no-win situation.

“Throughout these negotiations, the UAW has repeatedly offered responsible proposals and counterproposals to American Axle in an attempt to bring a conclusion to bargaining.”

The timing of the strikes could not be worse for GM, which in February reported the biggest ever loss for a carmaker in 2007.

Over the course of 2007 GM lost $38.7bn (£19.5bn) and recorded a fourth quarter loss of $722m.

As a result of these disastrous numbers GM was forced to offer voluntary redundancy to its 74,000 unionised workers in the US.