British police have begun a search for the gangmasters who employed 19 mainly Chinese shellfish gatherers who drowned on a beach in Morecambe Bay off the Lancashire coast.
Detectives said they would interview 16 survivors and continue looking for evidence in the bay, where the victims were caught by rising tides yesterday.
Politicians led calls for laws to be tightened in the murky world of gang labour, where gangmasters employ migrants, often illegally, to do poorly paid jobs.
"We must do something about these despicable gangmasters," Geraldine Smith, Labour MP for Morecambe and Lunesdale, told the BBC.
"We must make sure we take action to try and stop this sort of activity."
The victims, 17 men and two women, were cut off by rising tides in the treacherous flat bay, where the water rushes in faster than a person can run.
Police said some of them tore off their clothes to swim more easily and held hands in a desperate attempt to stay afloat.
Bishop of Lancaster Patrick O'Donoghue said self-regulation by the employers had failed. "The government must step in and set down legislation," he said.
Julia Hodson, Lancashire police's assistant chief constable, said those behind the tragedy were "criminals of the worst possible kind".
Ministers said gangmasters, who supply groups of cheap labourers to industries such as agriculture and construction, were covered by existing labour laws.
"Many of the people operating these sort of activities are ruthless and have little concern for the law," Minister for Work and Pensions Chris Pond told BBC radio.
Gangmasters said they would welcome a register and better regulation.
"We provide labour to the lower wage industry. I think indigenous, English folk don't want to do a lot of these jobs," one gangmaster told the BBC.
The British government said the bay holds more than six million pounds of cockles which are sold to restaurants in Spain and the Far East.