A senior government official has warned there could be a French Operation Stack if no new arrangements for customs checks are agreed by the time the UK leaves the EU.

Jon Thompson, the chief executive of HMRC, appeared before MPs on the Treasury select committee today.

He warned that while the focus had been on what could happen at Dover after March 2019 when the UK left the EU, there was equally a potential problem at Calais.

Asked by the Dover MP Charlie Elphicke which ports had the greatest potential for disruption, he said: “Our major concern is the closed loop system between Dover and Calais - it is the area where we are focusing most. The situation on the other side of the Channel is more problematic.

“Everyone is focused on Operation Stack, there is equally a risk of a French Operation Stack because you can’t get through Calais to get to Dover. While everyone is trying to leave Dover, you can’t get in so we need to make sure the system is balanced - it only takes two hours for everything to stop.”

But he said so far as the Treasury was concerned, there was no need to build additional infrastructure.

“Everyone is focused on Operation Stack, there is equally a risk of a French Operation Stack because you can’t get through Calais to get to Dover" - HMRC chief Jon Thompson

“We do not believe any additional infrastructure is needed for customs purposes at Dover. It is perfectly possible that other government departments may need additional infrastructure either in or around the Dover area.”

He also downplayed the prospects of Kent becoming gridlocked as a result of the possibility of no new customs arrangements being in place.

“There is an important question which needs to be wrestled with here which is whether - come 2019 - are French lorries carrying wine to Sainsbury’s any more risky in April than they were in March? In the initial phases, there is probably no risk at all. In which case, given the number of vehicles stopped at Dover is really small, does it make a significant risk at all?”

Hauliers are concerned that they could face long delays travelling to and from the continent as the UK’s departure from the EU will end the current system whereby no customs checks are needed.

Port bosses say that on average it could take 22 minutes to check each lorry coming in or going out.

Mr Elphicke said Brexit was a “massive national project” and said MPs should have a further hearing on the issue where evidence could be taken from other government departments.