Holidaymakers are stuck in "long queues" heading into the Port of Dover as French immigration controls reportedly caused a "critical incident" on Friday morning (22 July).
Doug Bannister, chief executive of the port, said "woefully inadequate" staffing in France was to blame for the disruption.
"Knowing we are now in a new world of post-Brexit and Covid checks, we worked to increase interim French border control booths by 50% and have improved traffic systems in order to build in resilience and capacity in time for the summer," he added.
"We have worked particularly hard, and extremely positively up to now, with our Police Aux Frontieres (PAF) colleagues over recent months to plan for the traffic volumes that were fully expected."
The port said it has shared traffic volumes in "granular detail" with the French authorities in order for the volumes to be matched by adequate border resource.
"Regrettably, the PAF resource has been insufficient and has fallen far short of what is required to ensure a smooth first weekend of the peak summer getaway period," Bannister added.
"We will continue to work with all Kent partners to look after those caught up in the current situation, which could and should have been avoided, and play our part in resolving it as soon as possible.
"Working with and through the UK government, we will also liaise constructively with PAF to work through the present logjam and to stress again the importance of adequate French border resource for the coming days and weeks on which we had previously been assured."
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