The Crown Prosecution Service (CPS) has previously warned that the “destruction of documents disables the authorities from establishing where an entrant came from, in order to increase the chances of success of a claim or application and/or to thwart removal”.

In its guidance to prosecutors, it admitted: “These offences have the real potential to undermine the whole system of immigration control.”

Alp Mehmet, the chairman of Migration Watch UK, which obtained the figures, said: “Verifying that those arriving in small boats are who they say they are is all but impossible given they have nearly all destroyed their documents.

“And yet, in most cases, we take them at their word and let them in even when there are serious doubts about their age and identity. This is a dangerous loophole that puts the public at massive risk. Most galling is that the government has known about it for years”

It is not just passports that are destroyed by migrants. Dan O’Mahoney, the Clandestine Channel Threat Commander,  told MPs: “Encouraged by the facilitators, [those crossing] will get rid of any sort of documentation or pocket litter, as we call it in law enforcement – phones, SIM cards, anything – before they are intercepted by Border Force.”

The Home Office data show the scale of the problem for the first time. In 2018, just 13 out of 299 (4.34 per cent) migrants arrived with a passport, falling to 1.1 per cent in the first two quarters of last year.

A Home Office spokesman said: “This Government is reforming our country’s approach to illegal entry to the UK and asylum by making the tough decisions to end the overt exploitation of our laws and UK taxpayers. 

 “The Government’s Nationality and Borders Bill will make it a criminal offence to knowingly arrive in the UK illegally and introduce life sentences for those who facilitate illegal entry into the country. We will seek to return people if appropriate even if they do not have official documentation.”