Britain inked a new deal with the bloc at a landmark summit in central London that marks a new chapter in UK-EU relations since Brexit on January 31, 2020.

The defence part of the agreement will allow British representatives to attend certain EU ministerial meetings and for its forces to take part in European military exercises and missions.

Asked for concrete examples, Lammy told AFP and a small group of European media outlets that he had visited Serbia, Kosovo, and Bosnia, and "there are concerns about the undermining of the Dayton Accords".

"We want to work closely with our European partners there," he said.

Lammy added that British soldiers were already "making a difference" in the Nato-led Kosovo Force (KFOR) peacekeeping missions.

"I think that it's hugely important that we are able to complement NATO," he said.

Lammy added it was "good" that the defence pact "opens a pathway" for British firms to tap into a 150-billion-euro ($168-billion) EU fund, currently under negotiation among the 27 member states.

An additional agreement still needs to be made, along with a financial contribution from London.

"We intend to get going quickly on this and hope that we can work this out in a matter of weeks," Lammy said of the next steps.

UK Prime Minister Keir Starmer's new agreement with Brussels also saw the two sides also agree to lift controls imposed on UK food and plant exports to the 27-country bloc.

That was agreed in exchange for Britain extending EU fishing rights in British waters, due to expire in 2026, for a further 12 years.

Lammy dismissed claims by the UK's opposition Conservative party that the deal meant Labour had "betrayed Brexit and Britain".

"My sense is always that the British people have moved on," Lammy said.

"I will let those in our political system who want to rehearse the fights of the past, they can do that.

"But in the end, we must be pragmatic on behalf of the British people, and this is a deal that delivers prosperity, security, fundamentally and is good for growth," he added.