(AFP) - British Prime Minister Rishi Sunak and French President Emmanuel Macron on Friday agreed a new pact worth over 500 million euros to stop illegal cross-Channel migration, at a summit in Paris aimed at forging a new start after years of Brexit tensions.

The deal will see Britain step up funding to France to allow hundreds more French police to patrol the Channel and also establish a new detention centre as a further deterrent.

Both leaders hailed a fresh beginning in relations between the two neighbours, after intense talks in Paris which were also marked by expressions of unity in their support for Ukraine in fighting the Russian invasion.

It was the first UK-French summit in five years, after Sunak became prime minister in October following the stormy tenures of Boris Johnson and Liz Truss marked by rancorous relations with Paris.

Macron said his talks with Sunak marked a "new start" while Sunak said it was "a new beginning, our entente renewed".

"We're writing a new chapter in this relationship," Sunak added, acknowledging the relationship "has had its challenges in recent years".

- 'No silver bullet' -

The centrepiece of the new atmosphere Friday was the deal to thwart illegal cross-Channel migration, a prime political priority for Sunak as he seeks to rescue the popularity of the ruling right-wing Conservative party.

London will step up funding to France over the next three years to total 541 million euros ($575 million), allowing the deployment of "hundreds" of extra French law enforcement officers along the Channel coast to stop the illegal migration, the British government said in a statement.

For the first time, the UK will help fund a detention centre in France to enhance its ability to cope with the number of people being trafficked across the Channel.

"We don't need to manage this problem, we need to break it," said Sunak.

"And today, we have gone further than ever before to put an end to this disgusting trade in human life."

The new funding from the UK this year is already more than double last year's package worth over 70 million euros that increased the number of French police patrolling Channel shores.

Sunak is under fierce pressure at home to reduce the number of asylum seekers arriving in Britain, and this week unveiled legislation that critics said would make Britain an international outlaw on refugee rights.

"There is no one silver bullet to solve this problem. So the legislation we introduced this week is incredibly important, cooperation with the French is important, illegal migration enforcement at home is important," Sunak said as he travelled to Paris on the Eurostar train.

But activists expressed unease over the plan, with the France director of Human Rights Watch Benedicte Jeannerod saying the sides were persisting with a tactic that "pushes exiles to risk dangerous crossings and subjects them to undignified treatment".

They said they were in complete agreement on helping Ukraine to defeat the Russian invasion and it should be Kyiv that chooses when any peace talks start.

"We want Ukraine to win this war. We are absolutely united on this," said Sunak.

Macron added: "Our desire is to help Ukraine to resist and to carry out the counter-offensives that it wishes to carry out. The priority of the moment is military."

- Bromance? -

Macron's distrust of Brexit figurehead Johnson was barely concealed, while Truss said she didn't know whether the French leader was a "friend or foe" during her campaign to become prime minister.

But both sides now see an opportunity to reset the "Entente Cordiale" between Western Europe's two nuclear powers.

"I hope it can be the start of a stronger relationship between us and it's a privilege to be able to play a part in that," Sunak told reporters as he travelled over.

As part of the British government's post-Brexit outreach, the summit paves the way for King Charles III to make France his first foreign destination when he heads there on a state visit at the end of March.

While Johnson revelled in French-bashing, Sunak says he and Macron are "friends", with their warm embrace during their first encounter in November sparking light-hearted speculation about a "bromance".

"It was not a summit like others. It was a summit of new ambitions," Macron said at the news conference.

© Agence France-Presse