Ministers are being urged by four UK charities to sign up to a new convention which guarantees help for the victims of human trafficking.
Thousands of women are trafficked and forced to work as prostitutes
The treaty, which will be discussed later at a Council of Europe summit in Warsaw, gives minimum levels of support and increased protection for victims.
It wants those trafficked to be seen as victims, not perpetrators, of crime.
The Home Office said it backed action on trafficking but no decision had been made on whether to sign the convention.
There are no reliable figures on how many people are trafficked to Britain each year, but the Home Office estimates 1,400 women were brought to the UK to work as prostitutes in 2000.
Men, women and children are brought to the UK not only for sexual exploitation, but as forced farm labourers and domestic slaves.
The four charities backing the campaign, Amnesty International, Anti-Slavery International, the National Federation of Women's Institutes and Unicef UK want victims to be given assistance.
The European Convention on Action Against Trafficking in Human Beings would give temporary residence permits to victims endangered by return to their home countries and to those who assist with prosecutions.
Under the convention victims would also be given a "breathing period" of around 30 days during which they would receive state support such as housing.
Anti-Slavery International's Beth Herzfeld said while Britain had outlawed human trafficking and was taking steps to fight it, there was no assistance for its victims.
The convention would ensure a minimum level of assistance was afforded to people who have been subjected trafficking, she said.
"What governments need to do is look at the issue in terms of the people whose human rights have been violated," she added.
The only assistance offered to victims is to those who were forced into sex work and agreed to co-operate in prosecutions, she said.
The charities highlight the fact there is no special assistance on offer for children.
Unicef UK's David Bull said smuggled children were abused, raped and exploited "right here in the UK" and that Britain should be first to sign up.
Yet there was still no safe house providing specialist care and protection for children, he said.
Mr Bull said: "Without this special protection children remain at risk even whilst in the care of social service departments."
Amnesty director Kate Allen said people were brutalised by the trafficking industry daily across Europe.
"Victims of trafficking have had all of their very basic human rights violated - we must turn the system around so that they are recognised as the victims and not the perpetrators of crime."
Men are trafficked and forced to work as farm labourers
The National Federation of Women's Institutes chairwoman Barbara Gill said her members believed trafficking of women and children was a "crime against humanity" and that "decisive action" needed to be taken now.
But the Home Office said while it "supported fully" the convention's aims, it included measures which might put more vulnerable victims at risk.
A spokesman said: "We too want to see widespread action to tackle this abhorrent trade at source, to protect and support the victims and bring those responsible to justice.
"This is why we will be using our presidencies of the European Union and the G8 to take forward work on trafficking.
"The convention contains measures which we believe may actively encourage people traffickers and may place more vulnerable victims at risk. We want to resolve these issues before taking a decision on signature."