A new system to protect trafficked children indicates that there has been an alarming rise in the number of Albanian child slaves forced to work in the UK.

If the trend – being highlighted on Anti-Slavery Day – were to continue, Albanians could soon outnumber Vietnamese children as Britain’s most exploited juvenile group.

Figures shared with the Observer by the children’s charity Barnardo’s – which is trialling a new Home Office-funded advocacy service to provide better protection for child-trafficking victims – suggest that a growing number of children from the former communist state are arriving in the UK, often voluntarily, only to end up being exploited.

“Within the past year there has been an increase in the number of trafficked children from Albania whom we support across our services,” said Javed Khan, Barnardo’s chief executive. He said some were used as forced labour, often on building sites, but most were exploited for criminal activities.

“We believe they have been trafficked internally after arriving here,” Khan said. “We know they have experienced trauma.”

The Home Office estimates that 13,000 people are believed to be victims of slavery in the UK. However, the true number of exploited children is probably significantly higher, Khan suggested. “We know the current estimate of the number of trafficked children in the UK is just the tip of the iceberg,” he said. “Due to the secretive nature of trafficking and inconsistency in collecting data across several agencies, it is difficult to definitively estimate the number of trafficked children in the UK. But we do know that many frontline professionals are not aware of the signs of trafficking.”

Barnardo’s is running a pilot service that sees trafficked children given a special advocate to look after their interests and to protect them from falling back into the hands of organised criminal gangs when they have been referred to social services.

Most of those helped were aged between 15 and 17, but the Barnardo’s schemes have encountered cases involving children as young as three. There was an almost even split between boys and girls. “It is common for young people to go missing in search of their traffickers,” Khan said. “This happens even after support has been put in place, due to threats by their traffickers. An independent advocate provides a single point of contact to the child, allowing them to build a relationship of trust and break the link with traffickers.”

An interim appraisal of the advocate scheme, being piloted in three regions in the UK, suggests that Albanian children comprise a quarter of all trafficked children being helped by the new service. They are second only to Vietnamese children – forced to work on cannabis farms and in nail bars – who make up more than 30% of the 160 cases overseen by Barnardo’s so far.

Five years ago Albanian children were not recognised as a particularly at-risk group in the UK. Most children forced to work as slaves in the UK came from Vietnam (31% of those recorded), Romania (16%), Morocco (16%) and Nigeria (13%).

Barnardo’s estimates that just over a third of the children it has helped are trafficked for sexual exploitation, while two-fifths were subject to forced labour. Almost one in 10 was made to go into domestic servitude, while 5% were forced into begging and petty crime.

In the last couple of years police have arrested large numbers of Albanians coming into the UK in lorries via the Channel ports. The new focus on the UK suggests that traffickers could be changing their tactics.

A report by the Protection Project in 2010 stated that: “In 2007, Greece was reported as the main destination for trafficked victims transited from or through Albania.”

The traffickers primarily use land routes and falsified documents to transfer their victims across borders. Kidnapping and deception of young women and girls for commercial sexual exploitation remains the main “recruiting” method used by traffickers. Once transported to the destination country, they are forced into prostitution and brutally abused.

Khan said it was a concern that the protection of trafficked children across the UK remained piecemeal. “We know that trafficked children are still going missing from care across the country as they are placed in inappropriate accommodation and denied the support to which they are entitled,” he said. “We urge the home secretary to establish legal powers for advocates so that they can compel public authorities to provide trafficked children with this support.”