The government has said it wants to see migrant boats intercepted at sea and directly returned to France in a bid to curb recent increases in Channel crossings.
Home Secretary Priti Patel has appointed a "clandestine Channel threat commander" who will work to make the route "unviable for small boat crossings".
Dan O'Mahoney, a former Border Force official and marine deployed to Kosovo and Iraq, will work with the French to explore what tougher action can be taken including "adopting interceptions at sea and the direct return of boats".
Britain wants Paris to stop more small vessels heading to England and take them back to French ports, rather than shepherding them onward until they reach British waters.
A government source told Sky News on Saturday that a "passive blockade" in the Channel was being considered, with the Ministry of Defence being asked for assistance by the Home Office amid reports the Navy could be brought in.
Immigration minister Chris Philp will meet his French counterparts next week as he seeks to shut down the Calais-to-Britain route completely.
It comes after recent calm conditions prompted a huge surge in people trying to make the journey.
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Kent County Council has said that 400 migrant children have been taken into its care this year, including 60 in the first week of August and 23 on Friday alone.
Ministers are believed to be looking at surveillance, reconnaissance and command controls as potential ways of reducing crossings.
But Helen Baron, a solicitor who is representing a number of migrants who arrived in the UK by boat, says the tactics are illegal and could risk lives.
"It's completely illegal under international law and it's deeply concerning that these kind of statements are coming out of government, they must know it's completely against the law", she said.
Former Labour shadow home secretary Diane Abbott commented: "The danger is that if you try and blockade these boats, which are mostly rubber dinghies and mostly steered by people who are not experienced sailors, then the boats tip over and people die."
But Ms Patel said: "The number of illegal small boat crossings is appalling.
"We are working to make this route unviable and arresting the criminals facilitating these crossings and making sure they are brought to justice."