Women and children brought to the UK as sex slaves will have new rights thanks to the government's decision to ratify the European convention on human trafficking.
Downing Street today confirmed Britain would join 34 other states in signing the treaty, which requires countries to provide victims with secure accommodation, access to emergency medical assistance, counselling and legal advice.
The convention also gives victims of trafficking a 30-day reflection period after they arrive in the country. Ministers had previously resisted signing the treaty because they believed this right to remain would be exploited by illegal immigrants.
The prime minister will make the official announcement tonight at a reception to mark the 200th anniversary of the abolition of slavery.
Shadow home secretary David Davis welcomed the news, which comes just days after he formally called on the government to ratify the convention. He said: "This is the right thing for Britain to do."
"However it needs to be accompanied by a series of practical measures such as the establishment of a UK border police force which would develop real expertise in combating this heinous trade.
"The prime minister also needs to address other failings such as how two-thirds of child trafficking victims who were rescued subsequently disappeared from government care."
Amnesty International campaigns director Tim Hancock also welcomed the news, saying: "Trafficking in people is a vicious and well organised crime which is causing untold human misery around the world and right here in the UK."
Signing the treaty would "end the uncertainty victims have faced in the past where they were not recognised as victims of crime and faced possible immigration detention and deportation", he said.
This weekend, the Catholic Bishops Conference pledged their support for the Conservatives' campaign to get the UK to sign the convention, saying that while Britain must be able to determine its own policy, an international problem need an international approach.
It said: "This year is the 200th anniversary of the abolition of the slave trade, an opportune time for the UK to show that it is committed to ending this modern form of slavery."
The government has already introduced a new office for trafficking for exploitation which carries a 14-year maximum penalty, and ministers are working with children's groups and Unicef to develop a coordinated approach to child trafficking.