By Sallie George
BBC News, Yorkshire
Campaigners have called for an end to modern forms of slavery
In the city where William Wilberforce helped abolish the slave trade 200 years ago, experts say slavery has made an "appalling" 21st Century return.
Researchers from Hull's Wilberforce Institute say thousands of migrant workers in the UK are being severely exploited by unscrupulous employers.
Many of them work under such a level of exploitation it meets the international definition of "forced labour".
"We are all compromised by slavery", Professor Gary Craig said.
The associate director of the Wilberforce Institute for the Study of Slavery and Emancipation (WISE) said in the Yorkshire and Humber region alone, there were hundreds if not thousands of people living and working in slavery conditions.
Sex slavery of women and children, as well as forced labour and debt bondage were all present in the region and across the UK, he said.
Prof Craig said: "Slavery is very much alive and well in Yorkshire today.
"In every city and every rural area of this region there are people who are working in slavery conditions."
WISE says there are thousands of modern slaves in the UK
Studies have put the net benefit to the UK economy of migrant workers at between £2bn and £3bn per year.
But Prof Craig said research showed these workers often worked for less pay, longer basic hours, with no sick pay, paid holiday, or written contract covering hours, conditions, pay and dismissal procedures.
Most were unaware of their rights and lived in "poor to appalling" accommodation, often six or more mixed-sex to a room, sometimes operating a "hot-bed" system, with workers sharing beds according to shift patterns.
In many cases, workers were forced deeply into debt by their employers and this, coupled with threats of violence, kept them working in "absolutely appalling", slave-like conditions.
There are up to 90,000 migrant workers in the Yorkshire and Humber region alone.
Prof Craig said: "All of us need to ask awkward questions.
"Are the newly-arrived migrants - serving us, supporting our job, working alongside us, living down the street - getting access to appropriate housing and employment conditions?
"If not, we should protest, complain, report.
"Many of us are too happy to enjoy the fruits of their labour but not pay an appropriate price for it."
Areas where exploitation occured ranged from agricultural work to food processing and packing, the catering and restaurant trade to nursing and domestic work.
Prof Craig said many large British companies relied on people working in slavery conditions to produce the goods they sold.
He said the complex nature of supply chains made it feasible for the company at the top of the chain to deny any knowledge of working conditions at the bottom.
Prof Craig said everyone needed to ask 'awkward questions'
But, he said: "It is barely credible for these big companies to say that they don't know about the conditions that people are working in."
The University of Hull's WISE researchers documented cases of exploitation for an extensive study into modern slavery in the UK, co-written by Anti-Slavery International and commissioned by the York-based Joseph Rowntree Foundation.
Dr Mick Wilkinson said he met a Latvian woman who had been charged £100 to sign up to an employment agency.
He said: "She was transported from Hull to Barnsley in a vehicle, she was then working eight-hour night shifts, she was sleeping two hours in the car and being woken up to work an eight-hour morning shift, and then transported back to Hull."
Deductions for administration and transport were made from her wages and any complaints were met with threats of being sacked and losing her accommodation.
"We are talking about people in these conditions who are regularly working 70 hours a week and are pocketing £50," Dr Wilkinson said.