Theresa May is facing new demands to stump up more cash for European migrant policing, with Belgium’s prime minister set to corner her at an EU summit in Salzburg in a bid to extract money.

Belgian media reports that Charles Michel, the country’s PM, will meet with Ms May at this week’s EU summit in Salzburg and ask her for a budget contribution similar to the one Britain already pays to France.

The backdrop to the latest demand is an ongoing political row in Belgium about so-called “trans-migrants” – who are increasingly travelling through Flanders on their way to the UK.

Faced with disquiet in his governing coalition on the issue, Mr Michel is dragging Britain into the row in an apparent attempt to unite his domestic parties by shifting the focus on to the UK.

He is expected to tell Ms May that since the migrants are destined for the UK and it is Britain who benefits from the border policing, it should pay the bill to keep them excluded from the country.

Downing Street confirmed a bilateral meeting was scheduled between the two leaders, but a spokesperson said they were not aware of the expected demands for money, which have been reported in a number of Belgian media outlets.

Though focus on the Salzburg meeting in the UK media has been on the limited Brexit discussion set to take place, the headline topic of the summit is actually about migration and security – with countries piling in to defend their interests on the issue.

The UK’s own National Crime Agency has already acknowledged that a crackdown on undocumented migration and people-smuggling in France has pushed activity into neighbouring Belgium, where people are now increasingly boarding lorries instead before travelling to the UK.

“In Belgium smuggling is prevalent. They are putting people on lorries in Belgium and then moving them across the border,” NCA deputy director Tom Dowdall told The Independent in July.

“They are loading up HGVs at stops and service stations. Some of the drivers are being duped but an increasing number are complicit [and being paid].”

The NCA says it is working with the Belgian authorities, as well as those of neighbouring France and the Netherlands.

Refugee crisis - in pictures Show all 27 1 /27 Refugee crisis - in pictures Refugee crisis - in pictures A child looks through the fence at the Moria detention camp for migrants and refugees at the island of Lesbos on May 24, 2016. AFP/Getty Images Refugee crisis - in pictures Ahmad Zarour, 32, from Syria, reacts after his rescue by MOAS (Migrant Offshore Aid Station) while attempting to reach the Greek island of Agathonisi, Dodecanese, southeastern Agean Sea Refugee crisis - in pictures Syrian migrants holding life vests gather onto a pebble beach in the Yesil liman district of Canakkale, northwestern Turkey, after being stopped by Turkish police in their attempt to reach the Greek island of Lesbos on 29 January 2016. Getty Images Refugee crisis - in pictures Refugees flash the 'V for victory' sign during a demonstration as they block the Greek-Macedonian border Refugee crisis - in pictures Migrants have been braving sub zero temperatures as they cross the border from Macedonia into Serbia. Refugee crisis - in pictures A sinking boat is seen behind a Turkish gendarme off the coast of Canakkale's Bademli district on January 30, 2016. At least 33 migrants drowned on January 30 when their boat sank in the Aegean Sea while trying to cross from Turkey to Greece. Getty Images Refugee crisis - in pictures A general view of a shelter for migrants inside a hangar of the former Tempelhof airport in Berlin, Germany Refugee crisis - in pictures Refugees protest behind a fence against restrictions limiting passage at the Greek-Macedonian border, near Gevgelija. Since last week, Macedonia has restricted passage to northern Europe to only Syrians, Iraqis and Afghans who are considered war refugees. All other nationalities are deemed economic migrants and told to turn back. Macedonia has finished building a fence on its frontier with Greece becoming the latest country in Europe to build a border barrier aimed at checking the flow of refugees Refugee crisis - in pictures A father and his child wait after being caught by Turkish gendarme on 27 January 2016 at Canakkale's Kucukkuyu district Refugee crisis - in pictures Migrants make hand signals as they arrive into the southern Spanish port of Malaga on 27 January, 2016 after an inflatable boat carrying 55 Africans, seven of them women and six chidren, was rescued by the Spanish coast guard off the Spanish coast. Refugee crisis - in pictures A refugee holds two children as dozens arrive on an overcrowded boat on the Greek island of Lesbos Refugee crisis - in pictures A child, covered by emergency blankets, reacts as she arrives, with other refugees and migrants, on the Greek island of Lesbos, At least five migrants including three children, died after four boats sank between Turkey and Greece, as rescue workers searched the sea for dozens more, the Greek coastguard said Refugee crisis - in pictures Migrants wait under outside the Moria registration camp on the Lesbos. Over 400,000 people have landed on Greek islands from neighbouring Turkey since the beginning of the year Refugee crisis - in pictures The bodies of Christian refugees are buried separately from Muslim refugees at the Agios Panteleimonas cemetery in Mytilene, Lesbos Refugee crisis - in pictures Macedonian police officers control a crowd of refugees as they prepare to enter a camp after crossing the Greek border into Macedonia near Gevgelija Getty Images Refugee crisis - in pictures A refugee tries to force the entry to a camp as Macedonian police officers control a crowd after crossing the Greek border into Macedonia near Gevgelija Getty Images Refugee crisis - in pictures Refugees are seen aboard a Turkish fishing boat as they arrive on the Greek island of Lesbos after crossing a part of the Aegean Sea from the Turkish coast to Lesbos Reuters Refugee crisis - in pictures An elderly woman sings a lullaby to baby on a beach after arriving with other refugees on the Greek island of Lesbos after crossing the Aegean sea from Turkey Getty Images Refugee crisis - in pictures A man collapses as refugees make land from an overloaded rubber dinghy after crossing the Aegean see from Turkey, at the island of Lesbos EPA Refugee crisis - in pictures A girl reacts as refugees arrive by boat on the Greek island of Lesbos after crossing the Aegean sea from Turkey Getty Images Refugee crisis - in pictures Refugees make a show of hands as they queue after crossing the Greek border into Macedonia near Gevgelija Getty Images Refugee crisis - in pictures People help a wheelchair user board a train with others, heading towards Serbia, at the transit camp for refugees near the southern Macedonian town of Gevgelija AP Refugee crisis - in pictures Refugees board a train, after crossing the Greek-Macedonian border, near Gevgelija. Macedonia is a key transit country in the Balkans migration route into the EU, with thousands of asylum seekers - many of them from Syria, Afghanistan, Iraq and Somalia - entering the country every day Getty Images Refugee crisis - in pictures An aerial picture shows the "New Jungle" refugee camp where some 3,500 people live while they attempt to enter Britain, near the port of Calais, northern France Getty Images Refugee crisis - in pictures A Syrian girl reacts as she helped by a volunteer upon her arrival from Turkey on the Greek island of Lesbos, after having crossed the Aegean Sea EPA Refugee crisis - in pictures Refugees arrive by boat on the Greek island of Lesbos after crossing the Aegean sea from Turkey Getty Images Refugee crisis - in pictures Beds ready for use for migrants and refugees are prepared at a processing center on January 27, 2016 in Passau, Germany. The flow of migrants arriving in Passau has dropped to between 500 and 1,000 per day, down significantly from last November, when in the same region up to 6,000 migrants were arriving daily.

In January of this year, Britain agreed to pay an extra £44.5m to France for policing at channel ports after Ms May came under pressure from Emmanuel Macron on the issue. The payments are a bilateral deal and are not dependent on Britain’s membership of the EU.

France had threatened to drop the Le Touquet deal – which allows British border controls to be sited on the France side of the channel – if the UK did not make a contribution to cover the costs of police work. Belgium also has so-called “juxtaposed controls” with UK passport checks conducted in Brussels for Eurostar passengers, albeit on a smaller scale.