The order for 200km/h dual-voltage (3kV dc and 25kV 50Hz ac) trains could be worth €3bn if all options are exercised. Deliveries are due to start in 2017, although Galant told the house it is "unlikely" any trains will enter service in 2017.

SNCB says it has nothing to add to the minister's comments and negotiations are continuing with the prospective suppliers.

The sets will be equipped with ETCS, which is due to be rolled out across the entire SNCB fleet by 2023 as part of Belgium's national ERTMS programme.

The order is a key element of SNCB's 2013-2025 investment programme, which seeks to increase fleet capacity to cope with growing demand.

SNCB already operates a fleet of 630 double-deck vehicles, comprising type M5 and M6 locomotive-hauled coaches. The M6 vehicles were also supplied by a consortium of Alstom and Bombardier, and the tender stipulates that the new EMUs must be compatible with this stock.