Sir Keir Starmer and Emmanuel Macron will hold talks at Downing Street as the UK pushes for France to do more to stop migrant crossings.
The French president arrived on Tuesday for the first state visit by an EU head of state since Brexit.
It comes as the UK has been pressing for tougher action from the French authorities on the beaches along the Channel coast.
The UK prime minister hopes to strike a “one in, one out” deal to send small boat migrants back to the continent, in exchange for the UK accepting asylum seekers in Europe who have a British link.
Alongside Downing Street talks, Mr Starmer and Mr Macron are also expected to attend a reception with UK and French businesses and an event at the British Museum on Wednesday.
Their spouses, Brigitte Macron and Lady Victoria Starmer, will have tea and a tour of Downing Street together, followed by all four having lunch.
While they are being hosted by Charles at Windsor, the Macrons will lay flowers on the tomb of Queen Elizabeth II and see Fabuleu de Maucour, a horse the French president gave Elizabeth in 2022 to mark her Platinum Jubilee.
In a speech to MPs and peers on Tuesday, Mr Macron promised to deliver on measures to cut the number of migrants crossing the English Channel, describing the issue as a “burden” to both countries.
He said France and the UK have a “shared responsibility to address irregular migration with humanity, solidarity and fairness”.
Decisions at a Franco-British summit on Thursday will respond to “our aims for co-operation and tangible results on these major issues”, Mr Macron added.
But he also stressed that Britain and France would “only arrive at the lasting and effective solution” if they addressed the “pull factors” encouraging people to make the journey across the Channel.
On Wednesday, Cabinet Office minister Nick Thomas-Symonds insisted that the UK was already working to reduce “pull factors”.
He told ITV’s Good Morning Britain: “That is why this Government is cracking down on illegal working and why there have been over 7,000 arrests in that space.”
Mr Thomas-Symonds declined to give a “running commentary” on negotiations with the French on migration, but told Times Radio that work with Paris was already “bearing fruit”.
The French denied a Telegraph report that Mr Macron blames the UK for the crisis.
A senior Elysee source said: “The French president looks forward to working with the Prime Minister constructively on this shared priority.”
Last week, the total number of people crossing the Channel in small boats this year passed 20,000.
The total now stands at more than 21,000, a record for this point in the year.
Mr Starmer and the French president are also expected to co-host a meeting of the “coalition of the willing”, the peacekeeping mission proposed to be deployed to Ukraine in the event of a ceasefire with Russia.
