General Secretary of the Aberdeen-based Oil Industry Liaison Committee (OILC), Jake Molloy, was speaking after documents were made public which he said showed the industry was still failing to address key safety issues.

BBC Scotland's Colin Wight reports on the union's fears

"Our concern is that all of the elements present in the run-up to the Piper Alpha disaster are as prevalent today as they were then," Mr Molloy told The Scotsman newspaper.

"I feel increasingly it is only a matter of time before we get a big bang and I don't want that to happen."

The OILC said the findings showed that operators were continuing to risk the lives of their employees, despite the lessons learned by Lord Cullen's inquiry into the world's worst offshore catastrophe in which 167 men died.

Safety systems

The documents are said to show that key maintenance programmes are being reduced in an attempt to cut costs.

BBC Scotland's Andrew Anderson hears the two sides in the safety debate

Safety checks on emergency systems, including deluge systems, gas detectors and alarms and lifeboat launching systems, are being curtailed, according to The Scotsman.

The papers obtained by the newspaper detail two reports on big gas leaks on two North Sea platforms this year.

Jake Molloy: "Big bang"

One had similarities to the initial leak that led to the series of fires and explosions which destroyed Piper Alpha.

The report on the release of gas on Shell's Cormorant Alpha on 6 April reveals that the gas flowed through a flange which had not been properly secured.

A report on a gas leak on Marathon Brae Alpha platform on 10 May discloses that gas entered its main control room as well as the temporary safe refuge for the workforce.

'General failure'

The confidential briefing note on the gas leak on Shell's Cormorant Alpha platform reveals that the platform had been shut down to enable a well from another platform to be tied into the topside facilities and to allow some maintenance to be done at the same time.

The report states: "There was a general failure to recognise when a series of smaller jobs had become a larger job requiring a more rigorous planning approach."

Shell says Cormorant A's systems worked

Documents relating to the programme of critical checks on safety systems on Shell's Brent Delta platform show that many are still outstanding, including tests on deluge systems, smoke detectors, gas detectors and alarms.

A confidential report on platform fire and emergency escape regulations for Shell's Brent Alpha platform shows that the number of examinations of vital safety equipment is being reduced from 236 to 88.

Oil director for Shell Expro, Chris Finlayson, said the Cormorant Alpha leak had been caused by human error.

"The safety systems did all react and the systems worked exactly as they were intended to. That cascade effect on Piper Alpha was not there and could never have been there," he told The Scotsman.

The Health and Safety Executive is due to announce plans to improve offshore safety this week.