A group of Moroccan, Algerian and Tunisian citizens were arrested in Dover last week by French border police while allegedly trying to travel to France while hidden in a lorry.
The migrants, numbering around 22 according to The Telegraph, had entered Britain legally on visitors' visas.
Migrants from French-speaking countries are increasingly making the journey to France via the UK, a British Border Force source said.
The route is a much safer option than navigating choppy waters in a rubber dinghy along the 30-kilometre journey through the Channel.
People from French-speaking nations are applying for UK visitor visas, “but in reality they don’t want to come here, they want to live in France,” the source said.
The source added that, despite entering the UK legally, “there is a possibility they are illegal entrants because they came here under false pretences.”
Migrants arrive in the UK after crossing the Channel unlawfully – in pictures
Announcing changes to the visa payment system in June, Simon Martin, the UK’s High Ambassador to Morocco, said Britain is a “popular choice” for people wishing to work or study abroad or visit.
“In the year ending December 2022, over 19,000 visas were issued to Moroccan nationals, a 65 per cent increase from the previous year,” he said.
A similar number of visas were given to Algerians during the same period, up 76 per cent from the previous year.
The trend of obtaining UK visas and travelling from Britain to the EU is believed to be a knock-on effect of stricter border checks on the continent.
Many of the bloc’s 27 member states have introduced more stringent measures amid concerns a lax approach to border security in the Schengen zone is making it too easy for migrants to travel unlawfully across Europe.
The EU is grappling with a massive increase in migration.
The number of people who have reached Italy via illegal means has doubled from 50,000 last year to 105,000 in the same period this year.
The government in Rome has ushered in new measures designed to curb charities' ability to pick up migrants drifting on flimsy boats in the Mediterranean. The approach has been criticised by NGOs.
Prof Andi Hoxhaj, a researcher on migration at University College London, recently told The National that the rate at which Europe looks for new agreements on migrant controls highlights the difficulties with such deals.
An EU deal with Morocco “must not be working, because otherwise they would not be exploring a new deal with Tunisia”, he said.