MPs are calling for a "full, independent public inquiry" into offshore helicopter safety amid fears that "a creeping complacency is affecting safety standards".
Offshore workers who raise concerns about helicopter safety have been told they should leave the oil and gas industry, said a report from the House of Commons Transport Committee
The MPs said there were concerned that "a regulatory inertia on the part of the European Aviation Safety Agency is leading to unnecessary risk for offshore workers".
Their report added that a recent review into offshore helicopter safety by the Civil Aviation Authority (CAA) had not looked at the impact of commercial pressure on helicopter safety.
Also, the CAA had not looked at its own role and effectiveness and, therefore, only "a full, independent public inquiry will have the resources, remit and power adequately to tackle those issues," the committee said.
The report said: "We heard troubling evidence about a macho bullying culture in the oil and gas industry, including that offshore workers who were concerned about helicopter safety were told that they should leave the industry."
The committee was looking into safety following the August 2013 accident in which four passengers were killed when a Super Puma helicopter crashed into the sea while on approach to Sumburgh airport in Shetland.
This was the fifth such accident involving the transfer of oil and gas industry personnel in the North Sea since 2009.
The committee's report said there was no conclusive evidence that Super Puma variant helicopters (which make up some 60% of the UK offshore helicopter fleet) were less safe than other helicopters.
But the MPs said that operators, manufacturers and industry safety groups should continue to engage with the offshore workforce to address their concerns in this area.
The committee said the CAA review of the Sumburgh crash found that since 2008 more incidents were reported in Norway than in the UK despite the Norwegian fleet being smaller.
The MPs said: "The CAA must conduct a joint review with its Norwegian counterparts to examine this disparity and report back within 12 months."
Launching the report today, the committee's chairman Louise Ellman said after the recent accidents " offshore workers' confidence in helicopter safety is understandably low".
She went on: "Despite work by the CAA, serious questions remain unanswered about offshore helicopter safety in the competitive commercial environment of the North Sea. We fear a creeping complacency may be affecting safety standards.
"The role and effectiveness of the CAA has not been adequately examined. Only a full and independent public inquiry would have the power and authority to investigate properly."
Mrs Ellman continued: "Survivors of the Sumburgh crash told us that they did not use the emergency breathing system provided on the helicopter because the information given to them by the safety video was flawed.
"It is appalling that it took a fatal accident in such circumstances before inadequacies in safety briefing were identified.
"Workers in the offshore industry have the right to know everything possible is being done to keep them safe. We call for the CAA to ensure that helicopter operators review all safety arrangements to guarantee all are fit for purpose."
Mick Cash. acting general secretary of transport union the RMT, urged the Government to accept the committee's recommendations in full.
He went on: "The tragic incident off Sumburgh in which four offshore workers lost their lives was an explicit illustration of how offshore workers' safety is compromised by helicopter operators who are not held to effective, industry-wide standards, including in the contractual relationship with their customers - the oil and gas companies.
"The committee recognises this and make the right recommendations to remedy what has long been an over-commercialised aspect of the industry."
Mr Cash continued: "There are now no excuses for the Government, helicopter operators or oil and gas companies. They must take clear and immediate steps to reduce the threat to offshore workers' safety from helicopter transport, reduce accident rates, improve survivability and listen to offshore workers' concerns about the safety of the helicopters they rely on."
Jim McAuslan, general secretary of pilots' union Balpa, said the MPs' report added " further weight to the urgent need for safety improvements to prevent accidents and make every offshore flight a safe one".
He went on: " Pilots are working with the CAA and operators to improve helicopter safety offshore and support the committee's call for a public inquiry.
"This should examine issues highlighted in the report including the safety risks of commercial pressure on operators and ensuring the UK regulator, the CAA, retains full control over regulating offshore flights rather than delegating to an ill-equipped European regulator."
A CAA spokesman said: "'Any loss of life in aviation accidents is always tragic and the safety of those who rely on offshore helicopter flights is therefore our absolute priority.
"In February we announced over 70 actions and recommendations to improve safety, primarily aimed at preventing accidents but also to improve survivability following an incident. These were widely welcomed by unions, helicopter operators, the oil and gas industry and Norwegian regulators and are bringing significant improvements in safety for those flying offshore in the UK and potentially worldwide."
He went on: "The new CAA-led offshore helicopter safety action group is ensuring operators and industry implement these changes as quickly as possible.
"Made up of the offshore helicopter operators, oil and gas industry and offshore workforce and pilot representatives, it has already overseen the approval of a new significantly enhanced underwater emergency breathing system for offshore workers.
"This new system will be rolled out across the UK offshore industry this summer and autumn with accompanying training.
"The CAA will ensure that safety improvements to UK offshore helicopter operations continue to be implemented as a priority."
A Department for Transport spokeswoman said: "It is vital that offshore workers are able to operate in a safe environment.
"We are working closely with the CAA, as the independent regulator, on this critical issue. We are grateful to the committee for its contribution and will respond formally to its report in due course."