Union leaders have expressed concern that a new law designed to make it easier to prosecute employers for negligently causing a death does not go far enough.

They said the families of workers who have been killed have been let down because the corporate homicide legislation, which came into force yesterday, only allows for the prosecution of companies, not individuals.

The act will apply where senior managers failed to take proper safety steps. Firms found guilty could be hit with much larger fines than any previously handed out by courts for health and safety offences. Companies could have to pay up to 10% of their annual turnover, or even more in the very worst cases.

However, Grahame Smith, general secretary of the Scottish Trades Union Congress, said the new law was a "fudge". "It is clear the governments in Westminster and in Holyrood have let down the families of workers killed by their employers," he said.

"This legislation will not allow for prosecution of individuals, but only of the company. Even then, only if the failures of a senior manager can be identified."

Privatised gas utility Transco became the first company in Scotland to be prosecuted under the common law crime of culpable homicide following a gas explosion which killed a family of four in Larkhall, Lanarkshire, in 1999. Andrew Findlay, 34, his wife Janette, 36, and their children Stacey, 13, and Daryl, 11, died in the blast at their house.

However, the charge of culpable homicide was later dismissed because the Crown could not identify a "controlling mind" who could be held responsible for the neglect.

Transco was later fined £15m - the largest health and safety fine to date in the UK.

A total of 31 workers were killed in Scotland in 2006/07, while a further 2702 were seriously injured, according to the Health and Safety Executive.