NORTH Sea oil workers who whistleblow about safety issues are routinely sacked, creating a "culture of fear" 20 years after the Piper Alpha disaster, one of Scotland's leading trade unionists has claimed.

The STUC has warned the practice could result in another disaster similar to Piper Alpha, which suffered a serious fire after an explosion caused by a gas leak that ignited on July 6, 1988, killing 167 people in the world's worst off-shore tragedy.

As relatives of the dead and some of the 61 survivors take part in a memorial service due to be attended by first minister Alex Salmond in Aberdeen today, the Sunday Herald can reveal the Health and Safety Executive (HSE) is investigating allegations that workers are told they are "not required back" - or NRB - after complaining about safety.

Ian Tasker, assistant secretary of the STUC, said: "While I would hate to think that Piper Alpha could happen again, or another serious incident takes place in the North Sea, I have my doubts.

"I have been told that some people who raise safety concerns are told all of a sudden when they are due to leave the platform or soon afterwards don't bother coming back.' "It suggests that some employers are not really interested in promoting good health and safety practices if they are willing to dismiss people who raise these issues.

"This practice is well known throughout the industry across different companies. The problem in proving it is that no company would admit it publicly happens."

Tasker claimed the culture is linked to ageing oil platforms - which he argues, should be shut down so that vital safety work can take place - and a system that encourages platform staff not to report potential hazards for fear of damaging their track records.

He said: "Companies operate behavioural reporting systems which reward employees if they go so many days without reportable accidents.

"It's something we need to get to the bottom of because, in the 21st century, it's a recipe for disaster if people are scared to raise health and safety concerns."

He added: "Some platforms are quite old and have been there since day one of North Sea oil production. They are concerned about how much money it will cost if they shut down production long enough for the repairs to take place."

"No matter what pressure is on oil companies to get the oil out of the ground, it cannot match the cost of human lives.

"The families of those who died on Piper Alpha have had to cope over the past 20 years with something which could easily have been prevented.

"Although the industry has moved on a lot, the age of some of the platforms and failure to fully engage with the unions and safety reps increases the risk of a serious off-shore incident.

"To lose so many workers in one incident was horrifying for the families involved. There have also been deaths since then and the impact on the families is just as horrendous. Sunday will be a hard day for the Piper Alpha families and anybody who has lost a loved one off-shore will feel for them."

Last week, Work and pensions secretary James Purnell demanded to know what improvements have been made after the HSE found wide variations in safety performance across the industry during a two-year investigation.

The report said that major accident risks did not seem to be well understood. The industry spent £1 billion improving safety after the disaster and the sum is spent every year on improvements.

Shell's UK operation was fined £900,000 in 2005 after admitting breaching health and safety regulations following an investigation into the deaths of two workers at its North Sea Brent Bravo platform. They were overcome by hydrocarbon gases, in September 2003.

Tasker described the failure to prosecute Occidental Petroleum, Piper Alpha's owner, as "the biggest crime" of the disaster.

Charles Woolfson, professor of Labour studies at Glasgow University, says it would have been unthinkable had the accident happened today.

He said: "We have moved a long way in terms of accountability in the past 20 years. I don't think the manage- ment and ownership of Occidental Petroleum would have been allowed to get away with what they got away with today."

Kit Carson, who predicted the Piper Alpha disaster in his book The Other Price Of Britain's Oil, said the safety cutbacks combined with the pressures to extract oil, gas and other resources throughout the world will lead to another major accident.

Carson, professor emeritus and an honorary research fellow in political science at Melbourne University, said: "It's a very important anniversary and my great sympathy goes out to those who lost loved ones, but what really worries me with the pressures to cut corners, whether it's in oil exploration or clean coal or gases, the risk of another Piper Alpha is still around.

"Lord Cullen's report into Piper Alpha found that responsibility for safety was in the same hands as the people who were responsible for rapid production of oil. There needs to be particular vigilance for the sakes of those guys who died and governments must not hold back on their responsibilities for forcing safety rules to be implemented."

Ian Whewell, the HSE's offshore head, said: "HSE is concerned that the apparent lack of justice for some employees involved in NRB situations strikes at the heart of the creation of the positive, constructive, safety culture necessary to deliver the standards of health and safety essential in such a high-hazard industry.

"Whilst the occasions where an employee is unfairly not required back' on an installation may be rare, it only takes one such case to seriously undermine the safety culture and create a climate where workers are reluctant to raise safety matters.

He added: "HSE has been talking with Oil & Gas UK and trades unions about how the NRB issue can be addressed and what needs to be done to reduce its potentially damaging impact on offshore safety culture."

The industry's trade association, Oil & Gas UK, said in a statement: "We would never condone the removal of any person, whether or not a safety representative, for raising safety issues. There may well be incidences where a contract has been terminated abruptly, but there is no evidence to suggest that this practice is widespread."