Channel migrants: Long-range camera can view Calais from Kent coast
Long-range thermal imaging cameras could be used to monitor migrant boats leaving France.
Leaked footage obtained by the BBC shows a trial of the technology taking place on the Kent coast.
The cameras allow Border Force officers to scour the coast of Calais from the cliffs of Dover.
The Home Office refused to confirm if it planned to purchase the equipment, which is similar to that used by US authorities at the Mexican border.
It said it does not comment on "operational matters of border security, including the allocation of such technology".
At least 858 people have crossed the Channel in small boats since November 2018.
A boat carrying eight migrants was intercepted by Border Force on Thursday after being spotted by a passing ferry.
Dover MP Charlie Elphicke said the cameras were "the kind of game-changing technology that we need to secure our borders".
He said it would allow boats to be "immediately seen, spotted, rung into the French authorities and apprehended".
'Lives at risk'
Lucy Moreton, general secretary of the Immigration Services Union, said the mobile camera units would not deter illegal migration, but would "assist with the preservation of life" in the Channel.
She said: "We can't see the French coast with sufficient detail to be able to prevent them setting sail, which is what we need to do to prevent them using this route into the UK.
"Once they are in the water they will refuse to be rescued... all the French can do is escort them into UK waters. They will put their lives at risk rather than agree to be rescued."
The Home Office said it had spent £1m on new security equipment since December 2018, with a further £2m "set to be spent on additional security measures to deter migrants".
Manufacturer FLIR declined to comment.