Keir Starmer has shown “great interest” in the Italy-Albania migration deal, the Italian prime minister, Giorgia Meloni, has said, as the UK vowed to send £4m to support her controversial crackdown on irregular migration.

Speaking at a press conference in Rome, the prime minister agreed with Meloni, stressing the importance of the relationship betwen the UK and Italy.

He indicated, however, that he was more interested in Italy’s strategy for stopping migrants from reaching the country than its deal with Albania, which is a few weeks away from completion.

The pair put migration at the top of their discussions during Starmer’s visit and were photographed joking and smiling in the gardens of the Villa Doria Pamphili in Rome.

The millions of pounds the UK will send to Italy will contribute to the Rome process, which is the Italian government’s project to tackle the root causes of irregular migration.

Meloni told the joint press conference: “No nation by itself can be effective in dismantling” the human trafficking network, and said they were looking at whether there was a “more structured way” for the two countries’ law enforcement agencies to work together.

Reflecting on their discussions about the Albania deal, Meloni said the “UK government has shown great interest in this agreement”, and both countries wanted “to enhance this very good relationship between Italy and the UK” and “increase co-operation with the EU while of course respecting the post-Brexit rules”.

Starmer said learning from the Italians on Monday marked “a return to British pragmatism”, and said the “remarkable progress” Meloni had made in reducing the number of illegal migrants was down to her “upstream work that tackles the issue at its source”.

“We’re pragmatists, first and foremost. When we see a challenge, we discuss with our friends and allies the different approaches that are being taken, look at what works, and that’s the approach that we’ve taken today. And it’s been a very productive day.”

A Downing Street spokesperson said: “The prime minister reflected on his visit to the National Coordination Centre in Rome this morning, accompanied by the UK’s newly appointed border security commander, Martin Hewitt. They agreed to take immediate steps to enhance our cross-border collaboration, learning from Italy’s success at reducing illegal migration by 60% in the last year through upstream work and enforcement.”

No 10 expressed concern about the treatment of people hoping to reach Italian shores who were instead left stranded in Tunisian deserts. The PM’s spokesperson said: “Obviously we take that incredibly seriously and want to be working more closely with countries upstream.

“The principles that we’ll be following in everything that we do is that it is workable, affordable and in line with international humanitarian law.

“But it is vital that we stop people from starting these journeys. We’ve seen far too many deaths in the Mediterranean as well as the Channel.”

Italy has faced accusations of violating the human rights of asylum seekers, in relation to its deal with Albania. Meloni rubbished the claims, saying: “I don’t know what human rights violations you’re referring to, to be totally frank.

“This accusation, I think it’s completely groundless.”

Starmer also announced Italian investments into the UK worth almost half a billion pounds, with Leonardo, one of Italy’s leading aerospace and security companies, investing £435m on their Yeovil sites, and Marcegaglia, a steel manufacturer, investing £50m in Sheffield to build a new clean steel electric arc furnace, creating 50 new jobs.

It came as the home secretary, Yvette Cooper, announced £75m in funding to increase the number of border security officers and crack down on people smugglers.

The cash injection will aim to deliver new technology and improve the capabilities of the UK’s Border Security Command.

Cooper said: “Criminal gangs are getting away with undermining our border security and putting lives at risk.

“State-of-the-art technology and enhanced intelligence capabilities will ensure we are using every tool at our disposal to dismantle this vile trade.”

The money originally allocated to pay for the previous government’s Rwanda scheme will be redirected to fund these plans.