The punishment over the rail crash, expected this week, comes as parliament considers a contentious proposed law on corporate manslaughter.

The long-awaited bill has left business at loggerheads with campaigners who say the reformed rules will let companies off too lightly and fail to hold individual managers to account.

The debate has highlighted considerations on either side that resonate beyond the UK. At its heart is a broad philosophical dispute over how companies should be made accountable.

Some campaigners for tougher corporate manslaughter laws argue for a two-pronged approach: individual officials should be held responsible, if possible, while companies should be prosecuted in cases of cumulative small failings.

Business representatives retort that there are few cases where problems can be traced back to one person - adding that existing health and safety laws are the best way to punish companies unless they are proved to be grossly negligent.

The government has brought the proposed law forward in an attempt to address longstanding and widespread criticisms that the existing corporate manslaughter law is inadequate for dealing with cases of alleged corporate negligence.

Prosecutions are rare and do not tend to target large companies or their officials. The high-profile prosecutions of big businesses have involved only fines under the health and safety law passed more than three decades ago. These have included the £11m fine on Network Rail and Balfour Beatty over the Hatfield crash in 2000 and the £15m fine on Transco, the gas supply company, over an explosion in Lanarkshire that killed a family of four in 1999.

The main reason for the lack of prosecutions of large companies under the existing manslaughter law is the need to find a senior company official who acted as a "controlling mind".

This makes it impossible to take on cases in which the company's negligence is the result of the collective errors of a number of officials, none of whom can be identified as the controlling mind.

In practice, this means that prosecution of large companies is not normally feasible: the only businesses for whom the controlling mind test can be proved are small, such as a company that ran a canoeing trip in Lyme Bay in 1993 in which four schoolchildren drowned.

Critics say the new bill neither holds officials sufficiently responsible nor goes far enough in enabling prosecutions to be brought against large companies.

They argue the proposed new law has been so watered down after corporate lobbying that it offers at most only a small improvement on existing law.

Louise Christian, senior partner at Christian Khan, the law firm, who has acted on behalf of people affected by train crashes, describes the proposed law as "pretend justice" and "a bit of a farce". She says its focus on fining companies rather than individuals will punish investors, who have no direct control over fatal incidents, while ignoring managers, who do.

A related and broader problem of accountability, say critics, is that company law still imposes no responsibility for health and safety on individual directors.

David Bergman, executive director of the Centre for Corporate Accountability, an advice and research group, says these requirements exist in countries such as Canada, Australia and in continental Europe.

Campaigners argue that another shortcoming of the bill is that it fails to give the courts enough options for punishments beyond the unlimited fines already available under health and safety law.

There is a provision for an "adverse publicity order" requiring a company to announce in the media the details of findings against it but critics say reforms should have gone further.

Possible measures - some of which are used in other countries - include community service-style penalties, director disqualification and remedial orders for companies to improve their practices.

The CBI, the employers' body, by contrast, says it is broadly happy with the "centre of gravity" of the bill and its focus on collective corporate responsibility.

John Cridland, deputy director-general of the CBI, argues against expanding the range of punishments available to the courts, which, he says, may not be the most appropriate bodies to issue orders relating to best management practice.

Nor is it true, he argues, that managers will escape responsibility under the new system: a large corporate fine would expose them to shareholder unhappiness.

Mr Cridland adds that it is incorrect to suggest business pressure has delayed the bill and undermined its effectiveness. The time taken to bring it forward reflects the evolution of the government's thinking, he argues. "They have realised the complexity of this," he says. "Great as it would be for me to take the credit for emasculating the bill, it would be very far from the truth."

If the bill does finally go through, the biggest threat facing big businesses may turn out to be reputational rather than financial or judicial. It would look much worse to be convicted for corporate manslaughter than for breaching health and safety regulations. An investigation alone could go on for years, generating extended bad publicity.

As David Leckie, partner at law firm Maclay Murray and Spens puts it, the bill may not save more lives in the workplace but it may still have consequences that cause companies to take notice of it. "It hasn't really changed much," he says. "What it has changed is the stigma."