Those firms found guilty face unlimited fines and loss of reputation.
From 6 April the Corporate Manslaughter & Corporate Homicide Act 2007 will see firms charged with manslaughter if the way they organise or manage activities causes a person's death and amounts to a gross breach of duty of care.
An organisation will only be guilty if the way in which its activities are managed or organised by its senior management is a substantial factor.
Kennedys partner Paul Carter said the Act's definition of senior management means that the actions anyone from site managers to chief executives could lead to prosecution.
"Prosecuting authorities will look at a much bigger slice of the workforce when considering whether the offence has been committed," said Carter.
"The inclusion in the definition [of senior management] of a person 'actually managing or organising … a substantial part of those activities' is…bound to catch a lower layer of management that, under the outgoing law, would not be classified as representing the directing mind."
Until now, there has only been a common law offence of corporate manslaughter. For a company to be convicted, two things must happen: an individual has to be found guilty of gross negligence manslaughter, and they had to be senior enough to represent the company's "directing mind".
While efforts have been made to prosecute big companies under the outgoing law – most recently in the Hatfield rail crash – all these attempts have failed.
Balfour Beatty and Network Rail escaped corporate manslaughter charges after the Hatfield crash. This was because prosecutors fail to identify one single person, "a directing mind", that was responsible for the failures which led to the accident.
But, they were still together fined £13.5M for health and safety breaches, and under the new manslaughter law any organisation found guilty will face an unlimited limited fine.