The delays started this morning, according to posts by the Port of Dover's travel updates account on social media.
At 7am on Sunday morning, it warned of a 25-minute wait at border control.
It said passport checks were having to take place manually due to an issue with border processing systems in France.
About 15 minutes later, it warmed the IT issues at French Police Border Control had seen delays increase to 45 minutes.
Shortly after 9am, it said there were delays of up to an hour.
