Sir Keir Starmer has wished Michel Barnier "all the best" after the former Brexit negotiator was named France’s new prime minister.
The announcement came on Thursday after more than 50 days of a caretaker government, during which president Emmanuel Macron scrambled to find a candidate to unite different sides.
A statement from Mr Macron's office announcing Barnier's appointment said he'd been tasked "with forming a unifying government to serve the country and the French people”.
"This appointment comes after an unprecedented cycle of consultations during which, in accordance with his constitutional duty, the president ensured that the prime minister and the future government would meet the conditions to be as stable as possible and give themselves the chances of uniting as broadly as possible," the statement said.
Sir Keir added: “We wish him all the best in his new role.
"The UK enjoys a strong relationship with France."
Here is all you need to know about Mr Barnier.
Who is Michel Barnier?
Michel Barnier is a staunch pro-European and a moderate career politician, though he toughened his discourse considerably during a failed 2021 bid to become his conservative party's presidential nominee, saying immigration was out of control.
Since 2015, he has been aligned to the centre-right party Les Républicains, which was founded by Nicolas Sarkozy, a former president.
Mr Barnier became a member of parliament aged 27, and later held roles in several French governments, including foreign minister and agriculture minister, though he has been out of political office in France for 15 years, spending most of that time at EU headquarters in Brussels.
On these shores, he is best known for being the EU's chief Brexit negotiator and leading talks with the UK government between 2016 and 2019.
He will be France's oldest prime minister since the Fifth Republic came into being in 1958. He takes over from the caretaker president, Gabriel Attal, who was the youngest.
Mr Barnier's political views are overall close to Mr Macron's, and it was crucial for the French president that his new prime minister did not try to undo reforms pushed through over the past years; in particular, pension changes that angered the left.
It remains unclear if Mr Barnier will fully try to implement Macron's political agenda or bring in new proposals. He will need to negotiate with other parties to get legislation adopted in parliament.
While Mr Macron had kind words for his appointee, his rivals to the left and right have hit out against the decision.
Leftist party the New Popular Front (NPF) leader Jean-Luc Melenchon said: "The president has just decided to officially deny the result of the legislative elections that he himself had called.
"It is not the New Popular Front, which came out on top in the election, that will have the prime minister... The election was therefore stolen from the French people. The message was denied."
Marine Le Pen, leader of the far-right National Rally, said: "[We] will not participate in a government of any kind whatsoever of Mr Barnier's.
"For the rest, that is to say on the fundamental issues, we are waiting to see what Mr Barnier's general policy speech is and the way in which he leads the compromises that will be necessary on the budget."
Mr Barnier married Isabelle Altmayer in 1982 and has three children.
