The scheme saw the removal of skin, bones and other body parts from up to 1,000 bodies without the permission of their families, which were then sold to biomedical supply companies for procedures like hip replacements.

One of the bodies that were used to take parts from is believed to be the broadcaster Alistair Cooke, best known for his Letter From America programme which aired on BBC radio for more than 50 years. Cooke died in 2004.

Undertakers are said to have made millions of dollars out of the plot that has been likened to "something out of a cheap horror movie".

Prosecutors said that the case has raised concerns that some tissue used in transplants could have been tainted.

Charles Hynes, Brooklyn District Attorney, said: "These ghoulish thieves thought they could pull off the crime of the century, stealing bones from the dead, without any thoughts of their victims' families or the transplant recipients who would receive possibly tainted bone and tissue grafts."

The seven funeral home directors entered their guilty pleas today in closed courtrooms. Their names have been withheld.

Defence attorneys said that among the suspects who are cooperating was the director of a funeral home that took parts from the body of Alistair Cooke.

Four other people in the case pleaded not guilty today to charges of illegally harvesting bones and organs, and have been released on bail. If convicted, they face up to 25 years in jail.

Michael Mastromarino, the owner of Biomedical Tissue Services of Fort Lee, in New Jersey, has been accused with three other men of secretly removing skin, bone and other parts from up to 1,000 bodies from funeral homes, without the permission of relatives.

The former oral surgeon is accused of making millions of dollars by selling the stolen tissue to biomedical companies that supply material for common procedures including dental implants and hip replacements.

Prosecutors said that they have unearthed evidence that death certificates and other paperwork were falsified.

X-rays and photographs of exhumed bodies show that white plastic pipes, like the kind used for home plumbing work, had been used to replace hip bones. The pipes were crudely reconnected to hip and ankle bones with screws before the legs were sewn back up.

In Mr Cooke's case, his age was recorded as 85 rather than 95 and the cause of death was listed as heart attack instead of the real cause - lung cancer that had spread to his bones.

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