Rail coaches destined for the Merthyr Tydfil line in Wales will be moved to England in a bid to save rail operator First Great Western (FGW) from losing its franchise.
The five Sprinter units - each made up of two rail coaches - were part of a £32m Welsh Assembly investment.
The trains will now be used in England, freeing up extra coaches for FGW's problem-ridden Cardiff-Portsmouth line.
FGW has been under fire over cancellations and overcrowding on the route, which prompted fare strikes by commuter groups.
The government has also criticised FGW for misreporting cancellations.
The National Union of Rail, Maritime and Transport Workers (RMT) has called for an end to the FGW franchise, saying it breached its agreement.
However, Transport Secretary Ruth Kelly gave FGW another chance, granting it a £29m help package, including the coaches formally destined for Wales.
Opposition members of the Welsh Assembly criticised the decision, saying Welsh railways were being deprived in favour of their English counterparts.
By Louis Makiello
