More than 400 national rail inquiry call centre jobs in Cardiff are under threat as it is confirmed a contract will not be renewed.
Serco had held the rail inquiries contract for seven yars
The Association of Train Operating Companies (ATOC) - which awards the contracts - confirmed on Wednesday that the Cardiff-based Serco would lose the contract it has held for seven years on 31 March next year.
ATOC has not commented on whether the three remaining companies competing for the contract propose operating the inquiry service from call-centres in the UK or overseas.
Rail inquiries chief executive Chris Scoggins was severely criticised last months when he said the service could be improved if outsourced to India.
Amicus, the union representing call centre workers responded by saying: "This attitude is an example of the idiocy of moving the inquiry service 10,000 miles away."
Union officials said that the time that if the inquiry service is moved overseas it could threaten more than 1,000 jobs around the UK.
"The impact could be devastating - hurting most the same communities that suffered worst from the collapse of manufacturing," a spokesman added.
A number of Western firms are sourcing Indian call centre provision
A statement issued by Serco read: "With a dedicated call centre in Cardiff, south Wales, that has consistently featured in the top list of quality measurements, Serco is disappointed not to have been chosen to renew its contract.
"Serco's bid was designed to continue the jobs of its call centre in Cardiff and to support the staff who have worked hard for the last seven years to make this a highly respected operation."
Unions have been battling against a tide of call-centre jobs being switched overseas, complaining about the loss of work in the UK.
Companies have been warned that their image suffers when they open call centres in other countries.
But many firms have been outsourcing jobs because of huge savings on labour costs.
A Serco spokesman said the company would negotiate to get a new contract in order to protect the jobs in Cardiff but added that there is no guarantee a new service provider will want to operate in south Wales.