The government is being urged to rethink its immigration proposals to protect victims of human trafficking and slavery at a time when large numbers of Ukrainians are fleeing the Russian invasion.
In a joint letter published in The Telegraph, 11 charities warn that the Nationality and Borders Bill "threatens to diminish protections" including statutory support for victims and a legal right to remain.
The letter was organised by Christian Action Research and Education (CARE) and is co-signed by 10 other groups, including International Justice Mission UK, and Women at the Well.
The publication of the letter coincides with the mass displacement of Ukrainians fleeing the Russian invasion of their country.
"The large numbers of refugees will provide conditions ripe for exploitation by those involved in human trafficking and modern slavery. Across Europe, criminal elements are poised to profit from the plight of displaced people," the charities warn.
They say that the government must do more to support trafficking victims and bring traffickers to justice. The letter also calls on the government to provide 12 months of statutory support for confirmed victims.
"We must act now to ensure proper support for both current and future victims of modern slavery," they write.
Nearly two weeks after Russia launched its invasion in Ukraine, the United Nations estimates that at least 1.5 million people have fled the country.
CARE has warned that Ukrainians fleeing the war are "at acute risk" of exploitation.
Lauren Agnew, CARE's human trafficking policy expert, said the situation in Ukraine was "hugely alarming" for those working to combat human trafficking. She expects to see a "disturbing spike" in trafficking cases.
"Governments across Europe must be mindful of the added dangers we now face," she said.
"People fleeing the conflict are arriving in Poland, Romania, Hungary, Moldova, and Slovakia. We know that criminal gangs are operating in these nations, waiting to traffic people across Europe and into the hands of exploitative industries, including in the UK.
"Traffickers prey on the vulnerability of displaced individuals, who they see as an opportunity to turn a profit. A crisis like Ukraine is a business opportunity for criminals."
She added, "We call on UK ministers to recognise the acute risk of exploitation the people of Ukraine face as they flee war and step-up efforts at home and abroad to challenge this heinous industry."