The number of people being used as "slaves" in the UK is increasing, according to the charity.
Hope for Justice, which campaigns against human trafficking, says the problem of forced labour, domestic servitude, and sexual exploitation is a "massive" problem in Britain.
Freedom of Information figures show that within the last three years 336 "slavery" offences were investigated by police in the UK.
Allan Doherty, of Hope for Justice , says the statistics are not a true representation of the problem. "On estimate it must be at least 10 times that, and that is just for the number of offences being investigated by law enforcement agencies."
"The actual number of trafficking victims is probably 100 times that again. Because at least 90% of victims probably never even come to the attention of authorities or charities such as ours because it's such a hidden crime."
The freedom of information figures show that out of 336 offences, 170 were investigated by the Metropolitan Police in London, and 88 in Scotland - both have dedicated human trafficking units.
One reason given for the low figure released under the Freedom of Information Act is the way in which crimes are recorded.
Often the more serious offence, such as rape or assault, is logged instead.
Hope for Justice also says that in the past front line services have not recognised the signs of trafficking but the situation is getting better.
Last year alone, the charity trained up to 700 police officers and social services staff to spot the characteristics displayed by trafficking victims.
In a statement the Minister for Slavery and Organised Crime, Karen Bradley, said the Government is doing everything within its power:
"to stamp out the evil in our midst".