British, American and other intelligence agencies from English-speaking countries have concluded a two-day meeting in London amid calls for spies and police officers to be given special, backdoor access to WhatsApp and other encrypted communications.

The meeting of the “Five Eyes” nations – the UK, US, Australia, Canada and New Zealand – was hosted by new home secretary, Priti Patel, in an effort to coordinate efforts to combat terrorism and child abuse.

Dealing with the challenge faced by increasingly effective encryption was one of the main topics at the summit, officials said, at a time when technology companies want to make their services more secure after a range of security breaches.

The meetings, however, were held in private with no agenda being made public, making it difficult to conclude exactly what had been discussed by the ministers, officials and intelligence agencies from the countries involved.

However, British ministers have privately voiced particular concerns about WhatsApp, the widely used Facebook-owned messenger service, which was used by, among others, the three plotters in the London Bridge terror attack.

“We need to ensure that our law enforcement and security and intelligence agencies are able to gain lawful and exceptional access to the information they need,” the Home Office said in a statement.

GCHQ, the UK agency which monitors and breaks into communications, has suggested that Silicon Valley companies could develop technology that would silently add a police officer or intelligence agent to conversations or group chats.

The controversial so-called “ghost protocol” has been fiercely opposed by companies, civil society organisations and some security experts – but intelligence and law enforcement agencies continue to lobby for it.

Police said they had not been able to see or crack open hundreds of WhatsApp messages sent by at least one of those involved in the London Bridge attacks because an acquaintance of theirs had refused to hand over his phone.

WhatsApp has also been improving its security after it emerged earlier this year that a flaw had been exploited by an Israeli spyware company, which allowed special software used by intelligence agencies to covertly take control of a person’s phone.

Ministers attending the event included Patel and the attorney general, Geoffrey Cox, who is the government’s most senior law officer. Also present was his US counterpart, William Barr.

Barr attracted controversy last week when he said the proliferation of what he described as “warrant-proof encryption” was making it easier for criminals to evade detection.

Patel described the summit as “an exciting moment for the UK” and said the UK was “a global leader on national security and child protection and we are committed to working with our close partners on shared challenges”.

The Five Eyes summit is an annual event, first held in 2013. The anglophone security network has become increasingly important at a time when the UK is planning to leave the European Union.