An MP has accused the French of waving migrants through with "a cheery bon voyage".
Responding to waves of migrants crossing the English Channel over the last few days, Tory MP Natalie Elphicke called France's handling of the situation "outrageous".
She tweeted: "This is simply outrageous. People who are perfectly safe in France brazenly break into Britain day after day.
"First it was a few, then hundreds and now heading towards a thousand in a single day. The French just waving them through with a cheery bon voyage."
It comes after reports that the numbers of people who made the journey reached 1,000 on Monday alone as warm sunny weather swept across the south coast.
The PA news agency has since reported that between between 740 and 750 migrants are believed to have arrived in the UK on Monday after making the journey from France in small boats.
Among them were several young children and a baby.
If confirmed, this could account for the second highest daily total of the year, following the single-day record of 828 people set last month.
Crossings continued on Tuesday, with eye witnesses reporting boats arriving in Dover while the RNLI was seen towing another ashore further east in Kingsdown.
At least 12,500 people have now made the crossing to the UK in 2021, according to data compiled by PA.
The perilous journey across the busy Dover Strait shipping lanes which separate Britain from the continent has claimed several lives, including that of a man from Eritrea last month.
The 27-year-old died after he and four other people jumped overboard as their boat started to sink as they tried to reach Britain.
The Home Office has repeatedly vowed to make the route "unviable", with Boris Johnson insisting that home secretary Priti Patel is "working around the clock" to address the matter.
Patel is expected to discuss the matter with her French counterpart Gerald Darmanin at the three-day G7 interior ministers' meeting in London.
Watch: Migrants rescued from Channel
Earlier this year, the UK and France announced an agreement to more than double the number of police patrolling French beaches.
It was the second pledge of its kind in a year, in a bid to prevent illegal migration and stop small boats from leaving France.
As part of the deal, the government pledged to give France £54 million to support its efforts to stop small boat crossings.
Patel has since told MPs she is prepared to withhold the promised funds unless there is an improvement in the number of migrants intercepted by French authorities, government sources confirmed.
It is understood that none of the money has been paid so far.
The prime minister's official spokesman said UK and French officials were "working on the implementation" of the deal and that "significant" funding provided in November had already led to increased patrols and "enhanced" intelligence.
He added: "Following a long period of poor weather, we have seen an increase in crossings as criminal gangs seek to exploit the improved sea conditions.
"This is still extremely dangerous. We remain determined to fix the broken asylum system and break the business model of people smugglers who put lives at risk, and welcome people through safe and legal routes."
Labour's shadow home secretary Nick Thomas-Symonds called for the government to focus on finding a "workable solution with the French authorities, tackling vile people-smuggling gangs and properly managing safe routes to prevent people risking their lives".
Watch: Record numbers of migrants reportedly crossing the channel