OGUK has revealed that 15% of the offshore industry's workforce - the equivalent of 65,000 jobs - have been lost since the start of last year; while North Sea investment by oil companies is expected to drop by up to £4 billion a year through to the end of 2018.

The OGA, which became an executive agency of the Department of Energy and Climate Change on April 1, issued a "call to action" six months ago when Brent crude was $US60/barrel. It's now sub-$US50, yet unit operating costs on the UK Continental Shelf are still higher than many other basins around the world.

"Last year, more was spent than was earned from production, a situation which has been exacerbated by the continued fall in commodity prices," OGUK CEO Deirdre Michie said.

"This is not sustainable and investors are hard-pressed to commit investment here because of cash constraints.

"The industry is under a lot of pressure and it is now widely recognised that a transformation in the way business is done is required if the UK sector is to become more resilient and competitive in a world of sustained lower oil prices.

"The sector has made a great economic contribution - having delivered production of 43 billion barrels of oil equivalent, paid over £330 billion in tax to date and supported hundreds of thousands of skilled jobs - and huge potential remains with over 20Bboe remaining to be extracted."

In a blunt warning, OGA CEO Dr Andy Samuel said that the UK offshore oil and gas industry needs to change "irrespective of the oil price".

Yet he remained optimistic.

"While the headwinds are strong, the expertise, imagination and tenacity of our industry and the people it employs are more than capable of rising to this challenge," Samuel said.

"The OGA is urgently working with industry and government to be a catalyst for this change and now is the time for everyone to demonstrate leadership."

Samuel warned that "we should be in no doubt about the scale of the challenge ahead; but it is important that we recognise the progress that has been made over the past six months and remain focused on the things that matter most as we look forward".

He said more work was needed to encourage companies to adopt more positive and constructive commercial, legal and operating behaviours.

The OGA plans to publish a five-year corporate plan at the end of this year which will set out its priorities and plans for delivering the sector strategies, and how the regulator will work with industry and government to realise maximum economic recovery from the UKCS.

It will include targets and performance indicators so that others can understand the OGA's approach and monitor its progress.