The UK and French governments must make a joint commitment to support struggling Eurostar, the chairman of the Transport Select Committee has said.
Tory MP Huw Merriman said the cross-Channel train operator plays a vital role in enabling low-carbon international travel.
Eurostar has been hit hard by the coronavirus crisis, with a 95% fall in passenger numbers.
It is running just one daily train in each direction between London and Paris, and between London and Amsterdam via Brussels.
The firm, which operated more than 50 daily services before the pandemic, revealed in November it is “fighting for its survival”.
Eurostar is 55% owned by French state rail company SNCF.
The UK Government sold its stake to private firms for £757 million in 2015.
SNCF chief executive Jean-Pierre Farandou told France Inter radio this week that “the situation is very critical for Eurostar”.
Merriman said: “We simply cannot afford to lose Eurostar to this pandemic.
“The company contributes £800 million each year to the UK economy.
“It is unique in offering an environmentally friendly, direct, connection to mainland Europe.
“Trips from London to Paris, Brussels and Amsterdam on the Eurostar emit between 80-90% less greenhouse gas emissions per passenger than the equivalent short-haul flights.
“Like airlines, quarantine and travel restrictions have blighted Eurostar’s access to its markets during the pandemic. Unlike airlines, Eurostar has been shut out from government loans that have offered a lifeline.”
He added: “It needs a joint, bespoke UK-French solution to help it through this crisis.”
Mr Merriman’s comments came after business leaders in London urged the Government to offer financial assistance to Eurostar.
Meanwhile, a French transport economist told the Transport Select Committee on Wednesday that he believes the UK will be asked to contribute to the survival of the operator.
Professor Yves Crozet, of the University of Lyon, said: “I suppose that the French government will support Eurostar, but not alone.
“We will have probably an arm wrestling between the UK and France about that.
“But clearly Eurostar is a subsidiary of SNCF, and SNCF has the majority of the capital. So clearly the money will come from France in a very important part but maybe France will ask the UK to give also some hand to the system.”