Romanian nationals were "treated like prisoners" while employed at a Carlisle car wash, a court heard.
Workers were deprived of breaks despite working up to 11 hours a day and were not provided with protective clothing, Carlisle Crown Court was told.
It is alleged they were housed in a dirty property and stopped from leaving after identity cards were taken away.
Three men - brothers Defrim Paci and Jetmir Paci, along with Sitar Ali - deny modern slavery charges.
One of the workers employed at the Shiny site, in Warwick Road, during 2016 and 2017 told of being left with a weekly wage of £10 after deductions for rent and electricity.
Another worker told police: "They treated me the same like they would do with a slave."
Prosecutor Martin Reid told jurors: "It is the prosecution case that the circumstances created by the defendants led to the freedom of the people that you are going to hear from effectively being overridden, and that they were compelled to work long hours, in bad conditions, for little pay.
"In short their liberty, their work was being exploited for the benefit of the defendants."
Defrim Paci, 40, of Windmill Close in Sutton-in-Ashfield, Nottinghamshire, is alleged by the prosecution to have "operated at the top of the conspiracy" but he denies any wrongdoing.
Jetmir Paci, 35, of Walton Walk in Boythorpe, Chesterfield, Derbyshire, admits carrying out some building work at the site but denies having any management responsibilities.
Mr Ali, of Adelaide Street in Carlisle, accepts he ran the car wash but denies exploiting workers, telling police he "treated staff well".
All three defendants deny two charges alleging conspiracy to require persons to perform forced and compulsory labour, and conspiracy to arrange or facilitate the travel of Romanian nationals to the UK with a view to exploitation.
Mr Ali denies a further charge alleging the possession of criminal property - namely cash.
The trial continues.