Tens of thousands of British citizens who pose a sexual threat to children online are increasingly seeking out victims in poor and war-torn countries, the nation’s top law enforcement agency has said.

The Philippines has become recognised as a commercial hub for child abuse imagery and live streaming of child abuse for foreign buyers. Children in Kenya, Cambodia, Vietnam, Thailand and other countries are also increasingly at risk as broadband access and free encrypted technology spreads across the world, the National Crime Agency (NCA) has warned.

“There is an increasing threat to children in developing countries where safeguarding capabilities cannot keep pace with advancing technologies, and this threat is likely to grow,” said Rob Jones, an expert on the sexual exploitation of children online for the NCA.

“We estimated that 80,000 UK nationals pose a sexual threat to children online – and this is a conservative estimate. What we know about offending pathways leads us to conclude that there are significant risks that many of these individuals will be taking advantage of the ready availability of free end-to-end encrypted technologies and inciting abuse through live streaming.”

Jones said it was impossible to know the number of children potentially at risk, but added: “If there are tens of thousands of potential perpetrators here, then children in countries around the world will also be targeted by offenders from elsewhere – the US, Canada and across Europe.”

Europol has identified live streaming of overseas child abuse, paid for and directed by westerners, as a key threat in the rise of global child exploitation.

The European crime agency said that mobile connectivity, growing internet coverage in developing countries, and the rollout of pay-as-you-go streaming, which provides a high degree of anonymity to the viewer, are furthering the availability and market for this type of abuse.

In the past decade, the Philippines has become a commercial hub for live-streamed child abuse, with webcam footage often paid for and facilitated by sex buyers thousands of miles away.

Many children are abused by their own families or neighbours, watched and directed by foreigners on smartphones, tablets or laptops.

Yet child protection experts are warning that this profit-driven model is being increasingly and rapidly replicated in other countries.

“Any country where there is high smartphone usage, where there are ways to transfer money quickly and relatively anonymously, and where there are high levels of poverty are likely to become places where children will be sought out,” said Jos de Voogd, spokesperson for Terre des Hommes, a Dutch child protection organisation.

“We have recently conducted work in Kenya, where we found that the problem of commercialised live-streamed sexual abuse of children to order is not only occurring, but rapidly rising. We are trying to assess the problem in Cambodia as well.”

There have been a growing number of prosecutions of British citizens for cyber sex crimes involving foreign children. Last year Alain Charlwood-Collings, a 39-year-old man from Devon, was sentenced to 18 years in prison, after it was proved that he paid £33,000 for more than 100 hours of recorded footage of the abuse of 46 different children in the Philippines. It took three years for the Philippine authorities to arrest those responsible for the abuse and recover some of the victims.

The UK arm of Every Child Protected Against Trafficking (Ecpat), an anti-trafficking children’s charity, said agencies like the NCA must be given the resources to tackle the growing commercialisation of online child sexual abuse, both here and in the countries where it is being perpetrated.

“Our concern is that here in the UK we have developed the technology to identify the perpetrators, but that it is harder to identify and locate the children thousands of miles away who are not being safeguarded,” said Bharti Patel, Ecpat UK chief executive.

“Agencies like the NCA urgently need to be given the resources they need to tackle these crimes, and help facilitate an international response in the country where this abuse is taking place.”

The NCA said that technology companies urgently need to be more proactive in preventing their platforms from being used to commit crimes against children.

“These live-streaming offences are technically enabled. Currently, anyone with a phone can do this,” said Jones. “Understanding the role of the networks we all use in this horrendous crime is the only way to combat this. Where there is vulnerability, paedophiles will seek it out, whether it is here in the UK or thousands of miles away.”

Jones said the NCA was working with law enforcement and government agencies across the world to ensure that perpetrators are sought out and prosecuted.

In August, the British government announced it was funding a cyber-security centre in Kenya to support the authorities in tracking down foreign paedophiles.

“This is a growing threat but this is being matched by a growing awareness, and we are currently working with 84 countries around the world to grow and develop our response to this,” said Jones.

“Let me be clear, if you are a British national or have British residency and are committing these crimes, we will hunt you down and bring you to justice, wherever you are or wherever your crimes are being committed.”