Coach firm National Express has said it plans to pull out of the consortium which runs the UK side of the Eurostar cross-channel rail service.
National Express finance chief Andrew Walker told the Reuters news agency that the company did not regard its stake in Eurostar UK as one of its core businesses.
"We won't be playing a part going forward," Mr Walker said.
National Express is the largest shareholder, with a 40% stake, in the company that has the management contract to run Eurostar UK.
The others are the French and Belgian state railways, with 25% each, and British national airline BA, with 10%.
News of National Express' withdrawal plans comes ahead of a restructuring of Eurostar aimed at transferring control over the service to a single company.
At present, ownership of Eurostar is split three ways between companies in each of the countries it serves - the UK, France, and Belgium.
The new ownership structure is expected to be in place by the end of the year.
Eurostar is facing tough competition from no-frills airlines Easyjet and Ryanair.
It has also been hampered by inadequate railway infrastructure on the British side of the tunnel, which has forced it to run its trains at slower speeds between the channel and London.
National Express shares closed 1.6% higher at 507p.