Eurostar has warned that leaving the EU under Brexit would pose serious questions about its capacity to operate as a viable business.

And bosses say that the impact of leaving would also create difficulties for other companies who rely on its service to conduct their business across the EU.

The warning comes in an uncompromising and blunt response to a Lords committee which is examining what the impact of Brexit could have on businesses.

In its written submission to the committee, the company makes clear it believes there will be nothing positive about leaving and doing so would create more difficulties for it across many areas of its business.

“Uncertainty could reduce inward investment, for example European entrepreneurs coming to London to start up. These would have serious implications for Eurostar as a business...” - Eurostar House of Lords submission

It highlights a series of concerns about recruitment, lengthier journey times, potential loss of investment from entrepeneurs and most seriously a decline in passenger numbers.

The submission says: “Eurostar has benefited immensely from EU rules making cross border rail travel easier and cheaper. If divergence between UK and EU rules were to happen, this would lead to significant cost and complexity for our business.”

“This in turn would affect our competitiveness and, depending on the nature of any differences between systems, it may not be possible to operate either from an economic or practical standpoint.”

The company is one of Kent’s most important businesses, employing around 1,800 people in the UK - of which three quarters are based at Ashford, St Pancras and Ebbsfleet stations and its London headquarters.

Last year, 10m passengers used its services, along with 350,000 British citizens living and doing business in France, Belgium, Germany and Holland.

On recruitment, it says: “More restrictive rules for employment of non UK nationals would make recruitment difficult and costly: a medium-sized company such as ours doesn’t have an HR department geared for complex employment processes.”

On the impact on other businesses who rely on its services, it states: “Uncertainty could reduce inward investment, for example European entrepreneurs coming to London to start up. These would have serious implications for Eurostar as a business.”

And on the issue of new border controls under a Brexit, it says passengers could face longer journey times:

“Experience suggests that removing juxtaposed controls and replacing them with “on arrival” controls would increase journey time by 40 minutes each way.”

"No. There are no benefits or growth opportunity that we could identify from leaving the EU" - Eurostar tells Lords' committee

It continues: “That is the equivalent of taking away the entire UK investment in HS1. The number of passengers using the service might be expect to fall significantly in such an eventuality, with a particular focus on time-sensitive business travel. Eurostar could not sustain such a re-alignment in its present form.”

And in an answer to the question of whether there would be any benefits by leaving, it is particularly direct, saying:

"No. There are no benefits or growth opportunity that we could identify from leaving the EU."

"As a cross-border operator, our fixed costs are already very high, and in many instances the business case is marginal."

"Any additional cost, small as it might seem, would only add to these costs and risks either raising prices for passengers or, if the market cannot bear such increases, making the operation unsustainable in its present form."