Is there something seriously amiss with the way health and safety breaches are investigated?

There are certainly questions to be answered about Scotland's comparatively low rate of prosecutions.

These have halved since a specialist unit was set up to investigate such offences. Scotland has a markedly lower rate of prosecutions than England and Wales, in spite of a proportionally higher rate of workplace deaths.

The Health and Safety Division of the Crown Office and Procurator Fiscal Service (COPFS) was meant to provide a "radical shake-up" of the way such cases were handled, improving their investigation and prosecution. But there were always concerns the unit would fall short of expectations.

Those concerns have been borne out. While the conviction rate is very high, at 98 per cent, many fewer cases are being taken to court.

The disparity raises serious questions: the number of health-and-safety-related prosecutions in England and Wales in the five years to 2014 was 27 times higher than in Scotland, even though its population is only about 10 times bigger. Given that Scots are more likely to lose their lives at work, albeit partly because they are more likely to be involved in riskier occupations such as fishing or the offshore oil industry, one might reasonably expect it to be the other way round.

So what is going on? Are we to believe there is more negligence about health and safety in England and Wales than in Scotland? That seems highly questionable. One obvious difference is that south of the Border, local authorities and the Health and Safety Executive (HSE) may bring court action, while in Scotland that decision rests solely with the COPFS, which uses its new specialist unit to investigate reported cases. The COPFS is simply prosecuting fewer cases.

The COPFS says these cases are often legally complex, but that has always been the case and so does not readily explain the sudden drop in prosecutions. It also insists it can only take forward cases that are reported to it, an implicit nod to the HSE. The HSE for its part says it submits cases to prosecutors that meet its enforcement criteria.

The HSE's dedicated staff are no doubt doing their best in the face of financial constraints, but an injection of money, enabling the organisation to expand its work, might help.

Critics, however, say the whole system needs to be overhauled, with repeated calls for health and safety legislation to be devolved, a sensible suggestion that should be adopted by the Smith Commission. There are already long-standing concerns about the serious shortcomings of Scotland's Fatal Accident Inquiries system, which also requires major remedial work.

It is hard to view these latest prosecution rates with anything other than dismay. A review of the work of the new specialist prosecution unit would help illuminate what has happened, but it has certainly not delivered what was hoped of it and that cannot be ignored.