Eurostar’s boss said its trains between the UK and Paris are carrying 30% fewer passengers.
Chief executive Gwendoline Cazenave said that with post-Brexit border controls and current levels of border staff, there was “congestion” at stations.
Eurostar currently operates 14 services a day between London and Paris, compared to 18 in 2019.
Ms Cazenave said the company may not restore some services suspended last year because of the problems.
“The issue now is that we are not able to run the same transport offer as we had before 2019 because of the bottlenecks at the stations,” he said.
“We have a major issue at the Eurostar terminals because of the new boarding conditions between the UK and the EU, because of the impact of Covid, because of the staff at the stations.”
Ms Cazenave also said Eurostar and the French and British authorities were working hard on solutions such as increasing border staff.
Last year, Eurostar announced it was ending its direct flights from London to Disneyland Paris and also stopped flights calling at Ebbsfleet or Ashford International stations.
It cited reasons that included financial problems due to losses incurred during the height of the pandemic and post-Brexit border controls – with more time needed to stamp UK passengers’ passports
Asked if services would be restored in the future, Ms Cazenave said: “We’ll see, it depends on how we can handle the big station issues.”
He said the company’s “aim” was “to be that backbone between big cities” such as London, Paris, Amsterdam and Brussels.
“These are the main cities, these are the main markets … we work, which I would say is our main role,” he said.
Currently, UK passengers traveling to the EU need their passports stamped when crossing the border, which has caused delays.
An Entry/Exit System, or EES, will replace the controls, but the technology has been delayed several times and is now due to be implemented in late 2023.
However, concerns have been raised that the initial sign-up for the scheme could cause delays to Eurostar services and lead to queues at the port of Dover, as under the scheme people entering the bloc from outside the EU – including the UK Vassiliou – they will need to register fingerprints and a photo with their passport details.
Once travelers provide their fingerprints and details, this registration will be valid for three years. During this period it must be validated every time someone crosses the border.
Ms Cazenave told the BBC Eurostar was “pushing” for the system to go completely digital, meaning people could enter details at home before they travel and that “it wouldn’t be a bad customer experience”.
“We know it’s a big deal, we know it’s a really big challenge,” he said.
The Eurostar boss said the system would still work without “digitisation”, but added it would take “a lot of investment, anticipation and staff.
On Tuesday, Eurostar announced its new brand, which included a merger between Thalys and Eurostar, and said it hoped to carry 30 million passengers a year by 2030.