The Home Office has denied it could have done more to prevent the deaths of 21 Chinese cockle pickers who drowned working illegally in Morecambe Bay.
Bags of cockles were all that was left behind
A gangmaster has been convicted of their manslaughter and local Labour MP Geraldine Smith said officials turned a blind eye to the issue.
"They were a low priority so they were just left to wander around," she said.
But Immigration Minister Tony McNulty said 3,000 police operations in two years had caught 150 criminal gangs.
The tragedy happened on the bitterly cold night of 5 February, 2004 off the Lancashire coast.
Two miles from shore the workers stood little chance when the tide came in and a rescue operation by emergency services found only one person alive.
Bodies were being washed up throughout the night but two other cocklers are thought to have died although their bodies were never found.
The gangmaster Lin Liang Ren, originally from China, tried to blame two of the dead men for what happened but he was convicted at Preston Crown Court of 21 counts of manslaughter.
The Edens said they should never have been prosecuted
He and his Chinese girlfriend and cousin were also convicted of helping the cockle pickers to break immigration laws.
A father and son from Merseyside were cleared of the immigration charge.
Mrs Smith, the MP for Morecambe and Lunesdale, said she had previously alerted ministers to the number of illegal workers in the town.
She feared further loss of life because a large number of cocklers had returned to work in the bay.
The court was shown an e-mail sent by the Home Office in 2003 which said: "The resource implications of arresting, interviewing and releasing such numbers are huge and simply not justifiable."
Mr McNulty said: "I would say to those who say that, were the Home Office and the government more reactive, this appalling tragedy wouldn't have happened - I'm afraid life's not as simple as that.
"We deal with illegal working as much as we can and in full, but there are other factors, like the willingness of the illegal workers themselves to assist us and we're trying to deal with things like that as well."
Liverpool businessman David Eden and his son, also called David, ran a company selling cockles.
They were cleared of breaching immigration law by employing illegal immigrants in connection with the tragedy.
David Eden junior said they had no knowledge the migrant workers did not have legal documentation.
He called for a public inquiry, blaming the government and police for the tragedy.
Legislation setting up the Gangmasters Licensing Authority was brought in after the deaths in Morecambe Bay and it will start its enforcement work next month.
Its chairman, Paul Whitehouse, said the new regulations were much tougher: "If you are not licensed and operating as a gangmaster you can be arrested and possibly go to prison for 10 years - that's just for not being licensed."