Offshore helicopter operations in the North Sea are to be reviewed, the UK's Civil Aviation Authority (CAA) has announced.

The review follows five accidents in the last four years, the last of which in August this year claimed four lives.

The CAA said the review will be undertaken jointly with the Norwegian CAA and the European Aviation Safety Agency (EASA) and advised by a panel of independent experts.

It will study current operations, previous incidents and accidents and offshore helicopter flying in other countries to make recommendations aimed at improving the safety of offshore flying.

The CAA said today: "Although there has been considerable effort by regulators, operators and the offshore industry to minimise the risk of North Sea helicopter operations there have been five accidents in the past four years, two of which tragically resulted in fatalities."

It added that the review would be led by the CAA's flight operations head Captain Bob Jones who will work closely with Geir Hamre, head of helicopter safety for the Norwegian CAA.

They will be supported by a team of experts who will consult with a wide range of individuals and organisations involved in offshore flying. The final review will also be subject to scrutiny by independent specialists.

The review will pay particular attention to:

:: Operators' decision making and internal management;

:: The protection of passengers and crew:

:: Pilot training and performance:

:: Helicopter airworthiness.

It will include a comparison study of UK operations with those in Norway. The findings of the review are due to be published in early 2014.

Mark Swan, director of the CAA's safety and airspace regulation group, said: "The recent accidents have understandably given rise to concerns, particularly with offshore workers who rely so heavily on these helicopter flights.

"We are absolutely committed to ensuring that operations are as safe as possible. The review we are announcing today will thoroughly examine the risks and hazards of operating in the North Sea and how these can be managed most effectively.

"We are extremely grateful to Geir Hamre from the Norwegian CAA and the European Aviation Safety Agency for joining the review team. They bring additional expertise and experience which will be invaluable to the review."

Last month's North Sea accident involved a CHC-operated Super Puma helicopter which crashed into the sea while on approach to Sumburgh airport in the Shetland Islands on the late afternoon of August 23.

Four oil workers were killed. There were 16 passengers and two crew aboard.

An interim report into the accident, issued on September 5 by the Air Accidents Investigation Branch, said that to date no evidence of a technical failure had been identified and that the investigation was continuing.

The aircraft had been coming from the Borgsten Dolphin platform when it crashed.

In April 2009, all 16 men on board a Super Puma helicopter were killed after it came down off Peterhead.

Earlier, in February 2009, all 18 people aboard a Super Puma survived after it ditched on its approach to an oil rig 120 miles from Aberdeen.

Two Super Pumas also ditched last year, with 14 people saved in an incident 20 miles north east of Aberdeen on May 10, while 19 people were rescued from the sea around 32 miles south west of Sumburgh airport on October 22.

All Super Pumas ceased operations for a time after last month's disaster but flights later resumed, with the version involved in that accident being allowed to fly on what has been described as "non-passenger revenue operations".

Bob Crow, general secretary of transport union RMT, said: "We welcome this CAA investigation but it should be seen as an addition and not a substitute for the full public inquiry that the RMT is demanding into the Super Puma tragedy in the North Sea on August 23.

"The RMT is also demanding an investigation into North Sea safety which extends beyond just the use of helicopters but which covers every aspect of the offshore working environment. Twenty-five years after (the) Piper Alpha (disaster) the industry owes its workforce nothing less than that."

Pilots' organisation Balpa said: "We will consult with those members currently operating in the North Sea as to their views on the effectiveness of a CAA-led review, but our immediate reaction is this is too little , too late.

"Firstly, the CAA has not shown itself adept at getting below the surface of industry, the real life experience of pilots and understanding the human factors that drive safety. Nothing in today's announcement gives us confidence that this has changed.

"Secondly, we believe a review needs to look at the totality of the commercial cut throat business that is the North Sea, and not just the helicopter operation. In short, just how high in the pecking order does safety really sit for an incentivised contract manager?"

Balpa went on: "Finally, we believe any review must look at the role of the regulator in this lengthening trend of accidents. We are, for instance, concerned that there does not appear to have been any pre-existing comparison of accident rates being maintained despite a series of accidents. In the light of this we just do not think it credible to expect the regulator to review itself.

"We have called on the Government to set up a judicial-led independent review along the lines of the post-Piper Alpha inquiry led by Lord Cullen. Today's announcement by the CAA does not do it for us."