In a letter to the Treasury and Department for Transport, they urge "swift action to safeguard its future".

Bosses of firms such as Fortnum & Mason signed the letter asking for access to government loans and business rates relief "at the very least".

The government says it is "working closely" with Eurostar.

The cross-Channel rail company is threatened by a large drop in passenger numbers due to coronavirus-related travel restrictions.

It reported in November that passenger numbers had been down 95% since March 2020.

With two trains an hour normally scheduled in peak hours, it now runs just two services a day from London to Paris and Brussels.

'Fallen through the cracks'

The letter, coordinated by business campaigning group London First and seen by the BBC, describes the firm as one that has "fallen through the cracks". Unlike some airlines, it has not been eligible for government-backed loans.

"If this viable business is allowed to fall between the cracks of support - neither an airline, nor a domestic railway - our recovery could be damaged," it says.

Co-signed by 28 leaders, including the vice-chancellor of Middlesex University, the chief executive of West End property company Shaftesbury, as well as the boss of the ExCeL conference centre, the letter points out that the company currently employs 1,200 people in the UK.

The firm is 55% owned by French state rail firm SNCF. The UK government sold its stake in the business to private companies for £757m in 2015.

The letter also credits Eurostar with reducing carbon emissions. Since it launched in 1994, it has transported more than 190 million passengers between Britain and mainland Europe.

A spokesman for Eurostar said: "Without additional funding from government there is a real risk to the survival of Eurostar, the green gateway to Europe.

He described the current situation as "very serious".

A spokesman for the Department for Transport said: "We recognise the significant financial challenges facing Eurostar as a result of Covid-19 and the unprecedented circumstances currently faced by the international travel industry."

He added the government had been in contact with Eurostar "on a regular basis" since the start of the coronavirus crisis and would continue to work closely with the firm.