Safety in the North Sea could be improved more quickly if helicopter firms volunteered to make changes, rather than waiting for regulators to take action, a new report says.

The Civil Aviation Authority (CAA) made a number of safety recommendations in February 2014 following a series of accidents involving offshore helicopters.

They included a ban on flying offshore in extreme weather, ensuring passengers are able to escape from emergency exits and fitting new breathing systems.

But in a newly-published report, the CAA said safety improvements "could be introduced more quickly through [...] operators voluntarily applying changes".

The watchdog said the same result could be achieved by intervention from the European Aviation Safety Agency or through contracts imposed by the oil and gas industry itself.

The majority of safety improvements brought in since the 2014 report have been as a result of direct action by the CAA.

But it said work towards introducing six safety measures recommended in 2014 has stalled, including standardising emergency exit windows, mounting flotation devices on the sides of helicopters and employing self-righting life jackets.

While most of these improvements could reportedly be implemented in less than three years, the CAA said it was "unaware of any voluntary activity in this area apart from work on handholds and revised push-out window pull-tabs performed by Airbus Helicopters".

There have been five serious offshore helicopter accidents in the UK over the last seven years, two of which were fatal.

Four people died when a Super Puma plunged into the North Sea near Shetland in August 2013 and 16 were killed in a similar 2009 crash off Peterhead.

The UK's Super Puma fleet was recently grounded following an incident in Norway which claimed 13 lives, including that of Iain Stuart from Laurencekirk, Aberdeenshire.