The discovery of three women allegedly held as slaves for 30 years is the "tip of a rather large iceberg", according to an MP in charge of reviewing evidence of slavery in Britain.
Frank Field, chair of the Modern Slavery Bill evidence review, said criminal gangs were making "huge sums of money" from people being imported into the UK to work "almost for nothing".
Speaking to BBC Breakfast, Mr Field said many victims who escape have no way of communicating because they speak little or no English and often come from countries where they are "deeply suspicious" of the police.
"We've had this example of domestic slavery but people are being imported to work, almost for nothing, in industry," he said.
"We've got begging gangs being developed, with people being imported. And of course we've got the whole question of how children are being imported to work. It's a whole range of issues we've got to wake up to."
Mr Field said it appeared the issue of slavery was getting worse as authorities were becoming more successful with prosecutions.
"If you think where other countries have started to be serious about this, the numbers have risen sharply," he said.
"I would have thought it's safe to act on the assumption that the examples we've had in the last few months are the tip of a rather large iceberg."
Slavery in the UK has not "been consigned to the history books," a Home Office minister said yesterday, as he warned that the emergence of such cases were likely to increase.
"We have seen increases year on year in the number of cases reported, and I expect that will continue to increase," James Brokenshire said.
"That's not necessarily because there are more of these cases, but more are coming to light.
The Modern Slavery Bill, which is due to published in the coming weeks, is designed to increase the penalty to life imprisonment and create an anti-slavery commissioner.
Mr Field said he hoped the creation of the new role of anti-slavery commissioner would become a "focal point" for the campaign to tackle the issue.
"It's so shocking to just be talking to people who have been through this," the Labour MP for Birkenhead said.
"It's incredibly brave that people have been able to talk about it. They themselves say the one thing they want from the bill above all others is a champion, a spokesman."
A man and woman, both 67, have been bailed following their arrests on Thursday in connection with the investigation into slavery and domestic servitude in Lambeth, south London.
The alleged victims - a 30-year-old British woman, a 57-year-old Irish woman and a 69-year-old Malaysian woman - are in the care of a specialist non-governmental organisation after they were rescued from a residential address last month.
It is thought that the 30-year-old woman had been in servitude all her life.
The case came to light after the Irish woman rang a charity to say she had been held against her will in a house in London for more than 30 years.
Scotland Yard has not revealed the nationality of the two suspects, who are non-British citizens, but said they have been in the country for "many years".
It emerged yesterday that the suspects, who have been bailed until a date in January, were previously arrested in the 1970s, although police have not said why they were detained.