Train company Connex could mount a legal challenge after being stripped of its South Central franchise by rail regulators.

Connex, which has run trains from the South Coast to London since 1996, lost its battle to carry on running the franchise last month.

The Shadow Strategic Rail Authority instead gave the franchise to Govia, which also runs the Thameslink service.

The two firms are competing to run the Thameslink franchise and an announcement from the regulator is expected next year.

Connex is now locked in talks with the authority's franchise director to discover why its bid was unsuccessful and if unhappy with the decision, it could mount a legal challenge to reverse it.

A Connex spokesman said: "We are continuing to work with the Shadow Strategic Rail Authority and when we are satisfied about the reasons why we were not successful and when we are happy with that we will begin discussions on the handover.

"An appeal of some type against the decision could be a possibility but we need to know the reasons first.

"This is the first occasion when an incumbent franchisee has not been selected to keep on running the service and I am not able to speculate on what could or couldn't happen.

"However, we definitely want to establish the detailed reasons for the authority's decision before we decide our next step."

An SSRA spokeswoman said a decision by its franchise director was final.

She said: "There is not an appeal process apart from the obvious route of going to court."

A total of nine companies have met the SSRA's pre-qualification critera to run the Thameslink Brighton to Bedford franchise. They include Connex and The Go-Ahead Group plc in conjunction with Via GTI, which formed part of the Govia bid.

Mike Grant, Franchising Director and Chief Executive of the SSRA said: "I am delighted by the very strong field of quality contenders we have assembled to submit proposals for these major new franchises.

"To secure either of these vital franchises, potential operators must table plans capable of delivering a step change in service quality. I will conduct an exacting competition, where innovation and investment will be important in reaching my final decision, as will track record.

"I am looking for strong, committed operators, capable of providing better service and good operational performance on these two important franchises."