The issue has gripped the UK's Home Office with a sense of urgency in light of Brexit and its anti-migrant politics.

"The effect of Brexit may be ultimately to reduce UK control of migration, not increase it," said Steve Peers, a law professor at the University of Essex, in a blog entry over the weekend on the issue.

But UK interior minister Priti Patel appeared determined to curtail the movements and demanded France take greater charge of preventing embarkations.

"The number of illegal small boat crossings is appalling," she said, in a statement.

Chris Philp, the UK's minister for migration compliance, made similar statements in an op-ed in the Daily Telegraph newspaper.

"We intend to return as many illegal migrants who have arrived as possible," he said.

Migrants seeking asylum are not 'illegal'

It is not illegal under international and EU law for people to enter a country without documents and then claim asylum or refugee status.

It means the notion of an "illegal migrant" falls flat, when that individual is seeking international protection.

Patel is also demanding genuine refugees claim asylum in France and other EU states instead.

People are not required to claim asylum or demand refugee status in a country deemed safe like France before first asking in the UK.

EU asylum law known as the Dublin regulation broadly requires the member state of first-entry to take charge of the asylum application.

But this does not prevent people from asking asylum elsewhere first and issues of family connection, especially when it comes to minors, may factor in on those decisions.

The UK had issued over 5,500 Dublin transfer requests in 2019, demanding other EU states take them back to handle applications.

It had also received almost 2,000 requests from other EU states over the same period.

The UK is also still bound by Dublin until the end of this year at which point a new agreement needs to be sorted with the EU.

Patel has since tasked a former Border Force official and marine to become the new so-called UK Clandestine Channel Threat Commander.

The idea is to make the route "unviable" for small boats attempting to cross the 33km-wide strip of water that separates mainland Europe from the British island-nation.

In a statement, the Home Office said it would "urgently explore tougher action in France."

France reportedly wants the UK to pay it some €33m for the effort.

The plan appears to prevent the boats from leaving in the first place, since forcing them back to France after they go to sea would be considered a "push-back", which is illegal.

The UK cannot also send patrol boats or other vessels into French waters without consent.

"System to return people not fit for purpose & once boats reach UK waters we're duty bound to help," noted Patel, in a tweet.

Some 45,000 applications for asylum were lodged in the UK in 2019. It had also granted some sort of protection status in 45 percent of the cases in 2019.

A bilateral treaty between the UK and France, known as Le Touquet, currently allows British border controls to take place in Calais as well as similar French controls in the UK.