“Border Force staff are feeling increasingly threatened. There is a risk of unrest from these groups,” said Ms Moreton.
“They are not exhausted, beaten down and glad to be here. They know they are going to be moved into accommodation. They want to be moved into accommodation. If that doesn’t happen promptly they get cross about it.
“They have to be clothed but we cannot provide hot food there. They might not have eaten anything. There is a mob mentality that takes over. The vast majority are young males. The families and children are moved clear very quickly.
“These are groups of people used to acting together to get what they need and frequently we cannot understand what they are saying to each other. The numbers arriving are phenomenal.”
The number of migrants reaching the UK in small boats this year is more than double the rate of 2020, which totalled 8,713, itself more than four times the numbers in 2019.
Over the bank holiday weekend, UK authorities dealt with 336 people in 19 boats on Friday and 144 in seven boats on Saturday. A further 17 crossed in one boat on Sunday and 71 people set out in three boats on Monday, bringing the total to 568.
The government has said it is cracking down on the criminal gangs behind the crossings. A Home Office spokesman said gangs were “putting profits before people’s lives”.
The department said more than 3,600 people had been prevented from crossing the Channel by French authorities so far this year.
Officials have secured more than 65 small-boat related prosecutions since the start of 2020, the Home Office added.