Home Secretary Priti Patel has said she wants the UK Border Force to be able to turn away migrant boats and send them back to France.
According to reports, border officials have already started training staff in “pushback tactics”.
The Home Office is understood to have taken legal advice that turning around some boats would be allowed under maritime law.
It comes after good weather saw a record-breaking 1,000 men, women and children attempt to cross the Channel in a single day on Monday.
Here Sky News explains what the government’s plans are and how they compare with existing international laws.
Border Force activity within British waters is governed by UK law, which has to comply with international maritime law – as set out by the United Nations.
The UN Conventions of the Law at Sea says that “every state” is required to “render assistance to any person found at sea in danger of being lost”.
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They must then “proceed with all possible speed to the rescue of persons in distress”.
But the law is not clear about what should happen “once a rescue has been effected”.
The UN’s High Commissioner for Refugees (UNHCR) claims the “definition of rescue implies disembarkation” on land.
But this is not specifically referred to in international law, so this may allow boats to be legally turned around, as long as their safety on land can be guaranteed.
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The Home Secretary has repeatedly said she wants to make illegal border crossings via the English Channel “unviable”.
In July she brought forward a new Nationality and Borders Bill, which she claims will help tackle the rising number of crossings.
If passed, it will increase prison sentences for people entering the UK illegally and – for the first time – consider whether someone arrived in the UK legally or illegally when potentially granting them asylum.
Specifically on migrant boats, Sky News understands that Ms Patel has asked Border Force to turn away some migrant vessels from British waters towards France.
The Home Office is understood to have taken legal advice that claims such tactics are in accordance with international maritime law.
Training of Border Force workers in “pushback” tactics is nearly finished, according to reports.
According to Oxfam, the term “pushback” refers to “the practice by authorities of preventing people from seeking protection on their territory by forcibly returning them to another country”.
Priti Patel is thought to have got the idea from recent visits to Australia and Greece, which both use it in their border policies.
According to reports, it is up to individual Border Force boat captains whether to turn a boat around or not.
Under maritime law they are only allowed to do so if it is considered safe – and if they can be sure the vessel won’t capsize as a result.
Several human rights groups have claimed that pushbacks are a breach of international law because they violate Article 14 of the UN Declaration of Human Rights, which states that everyone has the right to seek asylum from persecution.
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According to the advice taken by the Home Office, pushbacks are only legal if they can be done safely.
Smaller dinghies with large numbers of people on them are unlikely to fit this criteria.
A source told The Daily Telegraph pushbacks are likely to be restricted to “sturdier, bigger migrant boats” and only used in “very limited circumstances”.
The vast majority of the some 13,000 migrants who have attempted to enter the UK via the Channel this year have arrived in small boats.
This means that the legal use of so-called pushback tactics is likely to be very limited.
Priti Patel’s Nationality and Borders Bill makes a number of changes to the UK’s immigration and border policy.
These include giving life sentences to people smugglers and traffickers who facilitate illegal immigration into the UK.
Unveiling the bill, she said: “People who come from France, Germany, from safe countries around the world who then cross the Channel in small boats… they will not be able to claim asylum in the UK in the way that they have been able to for so long.”
Earlier this year, Ms Patel announced she was giving £54.1 million to France to help tackle spiralling migrant crossings.
She told the Home Affairs Select Committee: “We’ve doubled the number of patrols around French beaches and improved surveillance, technology and intelligence.”
But after accusations of wasting public money, Ms Patel has now threatened to revoke it, telling The Sun: “It’s payment by results and we’ve not seen those results, the money is conditional.”
There were also reports this summer that the Home Office had asked the Royal Navy to help deal with migrants in the Channel.
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The French have repeatedly refused to intercept or take back migrant boats.
Instead French vessels have often been seen assisting migrant boats into British waters.
The French interior minister has rejected the idea of “pushbacks”.
“France will not accept any practices that go against maritime laws, nor any financial blackmail,” he tweeted on Thursday.
“The UK must keep to their commitments, which I said clearly to my counterpart Priti Patel.
“The friendship between our two countries deserves better than these actions that harm the cooperation of our services.”
On Wednesday, French MP for Calais, Pierre Henri Dumont told the BBC: “Nothing can stop [the migrants].
“The fact is we’ve got 300 to 400km (186 to 248 miles) of shore to monitor every day and every night and it’s quite impossible to have police officers every 100 metres because of the length of the shore.”