The National Crime Agency (NCA) said it has seen some evidence of potential trafficking victims being marked with tattoos - like branding.
The report found that victims were marked with "various symbols signifying ownership or to show that a victim is over 18".
The report said it included the evidence to give front line responders another sign to look out for when dealing with potential victims.
By far the most common type of exploitation was sexual in nature. Other common exploitation types suffered by potential victims included:
- Sexual exploitation (41%)
- Labour exploitation (27%)
- Criminal exploitation (9%)
- Unknown (9%)
- Domestic servitude (8%)
- Organ harvesting (less than 1%)
Last year saw the number of potential trafficking victims from the UK more than double, according to a new report.
The potential victims came from 86 different countries. The most common countries of origin were:
- Romania (11%)
- Poland (9%)
- UK (7%)
- Albania (7%)
- Nigeria (6%)
The number of potential slavery victims exploited in car washes has risen from just seven cases in 2012 to 30 in 2013. Half of these were from Romania.
The National Crime Agency found that many of these were forced to work for low pay and bound to traffickers through debt bondage.
Of those trafficked for labour exploitation, most (around 10%) were put to work in the paving and tarmacking industry by members of the UK Traveller community.
There were also significant numbers being exploited in the agriculture, construction and food industries.
The number of potential victims of human trafficking who are British more than doubled to 128 last year.
The UK is now the Number One country of origin for trafficked minors, jumping ahead of Vietnam, Nigeria, Slovakia and Romania since 2012.
The most common form of exploitation for girls was sex, while for boys it was mainly labour or criminal purposes.
The sharp rise in British girls being potentially trafficked reflects growing awareness of the problem following reports into the abuses in Rotherham and Rochdale.
The term modern slavery was coined in 2013 to collectively describe the crimes previously known as human trafficking, slavery, forced labour and domestic servitude.
The Modern Slave Bill, introduced to the House of Commons in June 2014, will make it easier for authorities to pursue and prosecute individuals suspected of these crimes.
The number of children being trafficked for sexual exploitation has risen dramatically in the UK, according to estimates from police, government departments and other agencies.
The National Crime Agency's new report on the issue estimates that 602 children were potential victims of human trafficking out of a total of 2,744 last year.
Almost 90% of all the minors suffered sexual exploitation - more than triple the proportion seen in 2012.
The National Crime Agency warned that exploitation was well hidden, and that the real figures were likely to be much higher.
- If you believe someone is a victim of modern slavery you can contact the police on 101 or 999 if it is an emergency.
- You also report it at modernslavery.co.uk or contact the government's Modern Slavery helpline on 0800 0121 700.
The Government needs the public to become more aware of the plight facing modern day slaves so they can be freed and the perpetrators brought to justice, a Home Office minister told Good Morning Britain.
Karen Bradley admitted the Government did not "know the scale" of slavery in the UK and urged the public to "learn what to look for" via the Home Office awareness campaign.
A former slave has said she was too terrified to go to the police because the perpetrators told her authorities would only give them "a slap on the wrist".
The anonymous former slave told Good Morning Britain: "When I spoke to the individual and person she said, 'I bought you. I own you now.' If you do go to the authorities all we are going to get is a slap on the wrists and you will be deported."
According to the International Labour Organisation (ILO) 20.9 million men, women and children around the world are in slavery.
The most common forms of slavery according to the ILO are:
- Child Slavery affects an estimated 5.5 million children around the world.
- Early and forced marriage predominately affects women and girls who are married without choice, forced into lives of servitude often accompanied by physical violence and have no realistic choice of leaving the marriage.
- Forced labour affects people who are illegally recruited by individuals, businesses or governments and forced to work - usually under the threat of violence or other penalties.
- Descent-based slavery involves people who are either born into a 'slave' class or are from a 'group' that society views can be used for slave labour.
- Trafficking involves the transport of any person from one area to another for the purpose of forcing them into slavery conditions.