Home Secretary Priti Patel has reportedly defied French officials by instructing the Border Force to turn away migrant boats from British waters.
Several newspapers reported that officials are to be taught how to use "pushback" tactics to turn boats around under a plan to tackle rising migrant numbers.
Border officials will then be told to alert the French coastguard to the presence of migrants in their territorial waters, placing the burden on them for their rescue.
The reports suggest such turnaround tactics will only be used in "very limited circumstances" for sturdier, bigger migrant boats and only when deemed safe to do so.
To circumvent opposition from French authorities, Ms Patel is said to have ordered officials to rewrite Britain's interpretation of international maritime law, prompting anger from diplomats.
The Home Office has so far refused to confirm the reports with a spokesperson saying that "we do not routinely comment on maritime operational activity".
Earlier, at a G7 interior minister's meeting, she told her French counterpart that stopping illegal crossings was an "absolute priority" for the British public.
More on Migrant Crisis
UK talking to Ghanaian government about how it can help alleviate immigration problems, now-deleted tweet suggests
Migrants 'see the UK as El Dorado so they'll keep coming', say people in Calais
Migrant crisis: Record number tried to cross Channel to UK on Monday, say witnesses
Four toddlers and a baby among first migrant boat arrivals in UK after two weeks of poor weather
'It doesn't make sense' – migrant charity says asylum seekers are trapped in 'dysfunctional' system
Migrant crisis: Numbers trying to cross English Channel will get 'much worse', says ex-Border Force boss
Ms Patel and the French interior minister, Gerald Darmanin, held discussions on crossings at Lancaster House in London, in the wake of hundreds of migrants arriving in Kent over the past few days.
It comes as Sky News revealed that the UK is speaking to the Ghanaian government about a possible plan to alleviate the UK's immigration problems.
Witnesses claimed record-breaking numbers of migrants attempted to cross the Channel on Monday.
It was thought that at least 1,000 men, women and children were spotted making the journey from France to the UK, topping the previous high of 828 migrants on 21 August.
Although, the Home Office said the official figure was lower at 785 people, French authorities prevented 378 from reaching the UK that day.
Ms Patel tweeted that the talks were "constructive", adding: "I made clear that delivering results and stopping crossings were an absolute priority for the British people."
But The Times shed doubt on this, reporting that Mr Darmanin made it clear the proposals would damage relations and have "a negative impact on our co-operation".
Please use Chrome browser for a more accessible video player
Migrants arrive on Kent beach
Migrants arrive on Kent beach
The paper also said Mr Darmanin rejected a UK request to create a joint force, with police and border force officers from both countries patrolling the coastline and the Channel.
It said Mr Darmanin blamed the increasing numbers of migrants reaching the UK on new tactics deployed by people smugglers to "overwhelm" authorities.
He added that the pressure on France's borders "has never been greater".
French lawmaker Pierre-Henri Dumont, who represents the Calais region of northern France, said authorities there were doing all they could.
"The fact is, we've got 300 to 400km (190 to 250 miles) of shore to monitor every day and every night, and it's quite impossible to have police officers every 100m (330ft) because of the length of the shore," he told the BBC.
"We cannot stop all the crossings," he added. "We need to address the causes of migration."
Ms Patel is under increasing pressure from Boris Johnson and senior Tories to stop the flow of people from Calais.
She has threatened to withhold millions of pounds in funding to help France bolster their coastal patrols unless the number of migrants intercepted by them improves.
Earlier this year France and the UK agreed to double the number of police patrolling French beaches, with the UK promising £54 million in support.
But the two countries have clashed over their interpretation of maritime law.
France says it states that the coastguard is barred from intercepting boats unless those on board request assistance.
On Wednesday, Prime Minister Boris Johnson said efforts to stop the crossings depended "to a large extent" on the ability of the French authorities.
Data compiled by the PA news agency suggests at least 13,000 people have now made the crossing to the UK in 2021.
According to the UK government's clandestine channel threat commander Dan O'Mahoney, efforts so far have prevented more than 10,000 migrant attempts, led to almost 300 arrests and secured 65 convictions.