The UK will pledge an additional £44.5 million to strengthen Britain's border controls in Calais and other French ports, including fencing, CCTV and detection technology.

Theresa May is to make the announcement during talks in Berkshire with President Emmanuel Macron on Thursday.

Macron has reportedly pressed the prime minister in recent weeks to increase funding for security, and to take in more refugees.

"This is about investing in and enhancing the security of the UK border," a Government spokeswoman said.

"Just as we invest in our borders around the rest of the UK, it is only right that we constantly monitor whether there is more we can be doing at the UK border controls in France and Belgium to ensure they are as secure as possible."

May and Macron will meet at the Royal Military Academy at Sandhurst, with the leaders expected to discuss increasing co-operation on defence and counter-terrorism, despite Britain's impending withdrawal from the European Union.

The talks will also witness the first meeting of the heads of the two countries' main intelligence agencies, with MI5, MI6, GCHQ and France's DGSE and DGSI in attendance to discuss collaborating in the fight against terrorism.

Britain will also commit to Macron's "European intervention initiative," a plan to better coordinate armed forces from different nations.

May also wants to discuss the "very significant" proposals by the French to loan the Bayeux Tapestry to Britain, where it has never been displayed.

Macron's focus on border issues, however, was underlined by a visit to Calais on Tuesday when he vowed there would be no return of the infamous migrant "Jungle" tent city which was cleared by the authorities in 2016.

UK funding for security in the region is thought to have topped £100 million over the last three years, while more than 750 children have been transferred to Britain since the Jungle was shut down.

British officials said the new UK funding would build on previous security work in the area, pointing to figures showing illegal attempts to enter the UK fell from more than 80,000 in 2015 to just over 30,000 last year.

Up to 7,000 men, women and children lived in the Jungle in Calais before the site was cleared in 2016. But hundreds of asylum seekers hoping to cross the Channel remain in the area, more than a year after authorities dismantled the sprawling site.

Speaking ahead of the meeting, May said the summit underlined the "broad and unique nature" of the relationship between the two countries.

"Today's summit will underline that we remain committed to defending our people and upholding our values as liberal democracies in the face of any threat, whether at home or abroad," she said.

"What is clear from the discussions we will have today is that a strong relationship between our two countries is in the UK, France and Europe's interests, both now and into the future."