LONDON — They lived in desperate straits in Poland, often homeless and suffering from addictions. So when the call came to get free housing and well-paid jobs in Britain, hundreds decided to make the move.

But instead of a better life, the British authorities said on Friday, the immigrants found themselves in the clutches of a human trafficking ring that lured workers to England, starved them, crowded them into squalid housing, forced them to work long hours at menial jobs, stole their wages and paid them as little as £10, or about $12, a week.

Eight of the group’s members, all of them Polish, have been found guilty in a Birmingham court of trafficking and forced labor, in the “largest ever modern slavery prosecution” in Britain, the Crown Prosecution Service said in a statement. The ring may have victimized as many as 400 people over several years, prosecutors said.

Five of the defendants were sentenced earlier this year to prison terms ranging from four and a half to 11 years, and three others are awaiting sentencing. While some of the convictions occurred months ago, reporting restrictions on the case meant that details were not made public until Friday.