The contested deal, worth around CHF2.1 billion (US$2.6 billion), is for the construction of 116 new regional trains that will enter service in the 2030s, chiefly on the Zurich regional railways and replacing double-decker trains that have been in service around Switzerland’s biggest city since 1990.

In a statement published yesterday, Stadler said it “cannot understand” the decision to award the contract to Siemens and has lodged an appeal with the Federal Administrative Court.

“The price difference compared to the winning bid is only 0.6%,” it added.

Stadler employs 6,000 people in Switzerland and the decision to award the contract to its competitor has rankled other actors in the country.

Unia, a trade union, said the decision was “incomprehensible” and maintained that more than “170 Swiss subcontractors” could have contributed to the project if Stadler had won.

The Swiss Federal Railways (SBB), which awarded the contract to Siemens in early November, said in a statement it would “take note” of Stadler’s response.

However, it added that its German counterpart had “clearly submitted the most advantageous offer”.

“The price difference mentioned by Stadler Rail concerns only investment costs”, while the true gap amounts to “hundreds of millions of francs” when operating costs over 25 years are considered, it said.

SBB’s director general has received death threats following the contract’s announcement, the paper SonntagsBlick has reported.

Active in Switzerland since 1894, Siemens Mobility also employs 6,000 people there.

The German group said in a statement that it has noted the appeal but is “confident” it submitted an “attractive” offer.