The UK Government has unveiled a radical plan aimed at rewarding investment in the North Sea in a bid to see as much oil and gas extracted as possible.

A review of the fiscal regime for the oil and gas sector was announced in this year's Budget, with a new Treasury report saying "significant change" was needed in order to continue to attract investment.

Chief Secretary to the Treasury Danny Alexander launched the new report as he met key industry figures during a visit to Aberdeen today.

There is still "significant hydrocarbon reserve" in the UK Continental Shelf (UKCS), the Government said, which could "generate significant benefits for the UK" if it can be recovered.

It estimated there could be up to 21 billion barrels of oil equivalent remaining offshore, and the report said industry experts believe some 15 billion to 16.5 billion barrels are economically recoverable.

The UK Government's response to the review said: "Offshore production will continue for many decades to come."

But it added that operators in the UKCS are "facing strong competition for scarce investment whilst the economics of the basin have changed fundamentally".

It said there were also "opportunities to simplify the fiscal regime to provide greater certainty, lower administrative burden and fewer distortions".

The report continued: "The Government's view is that current levels of investment cannot be maintained without fiscal change. The trend towards smaller fields and higher costs implies that typical projects in the UKCS will struggle to attract investment in a competitive global environment. Now is the time to make that change to ensure the UKCS can compete for global capital.

"This document therefore sets out a radical plan for reform of the fiscal regime. The reforms are designed to support the Government's twin objectives of maximising the economic recovery of hydrocarbon resources whilst ensuring a fair return on those resources for the nation."

Key in the reforms is an immediate cut in the rate of the supplementary charge on oil industry companies' profits, from 32% to 30%, which was announced by Chancellor George Osborne in his Autumn Statement yesterday.

The UK Government also plans to introduce an investment allowance, which it believes will reduce the effective tax rate further for companies investing in the North Sea.

Financial support will be provided for surveys in under-explored areas of the UKCS, with the Government to work with the industry for options on shared funding.

Meanwhile, options to improve access to decommissioning tax reliefs are to be developed

"Together, these measures represent a radical plan to reward investment in the UKCS at all stages of the industry life cycle," the Treasury report said.

"These reforms will make the fiscal regime more competitive, simpler and more predictable, and represent the most balanced and investment-focused way to move to a lower tax burden over time. They will support billions of pounds of investment throughout the life cycle of fields."

But it stressed: "Action by Government must be matched by action by industry and the Government expects the industry to make significant improvements in production operations, in improving its cost-efficiency and in commercial practices in line with the objective of maximising economic recovery."

The new industry regulator, the Oil and Gas Authority, will be asked to monitor and report on the sector's progress in these areas.

Mr Alexander hailed the North Sea oil and gas sector as being "one of the country's greatest industrial success stories", stating: "It remains the largest industrial investor, provides just over half of the UK's primary energy needs and supports hundreds of thousands of jobs."

But in the foreword to the report, he said: "The oil and gas remaining is becoming increasingly difficult and expensive to extract and shifts in the global oil and gas landscape may make it harder to continue to attract global capital without substantial improvements in the fiscal and regulatory landscape."

He said that was why the Chancellor had announced a review of the fiscal regime for the industry, and added: "This document sets out the conclusions of that review: a radical plan to reward investment in the UKCS at all stages of the industry life cycle.

"It recognises that to maximise investment we need to reduce the overall tax burden facing the industry, and sets out long-term principles for the future that we believe the Government and industry can both buy into as well as specific actions to ensure a more competitive, simple and predictable fiscal regime."

Speaking in Aberdeen, Mr Alexander said: "I have always been an advocate of Scotland's thriving oil and gas industry, which is why I'm here today announcing the Government's ambitious package to continue to support this hugely valuable sector.

"We're incentivising and working with the industry to develop new investment opportunities and support new areas of exploration. This will help ensure that the industry continues to thrive and contribute to the economy. This level of support is only possible because we can draw on the combined strength and resources of the United Kingdom."

Exchequer Secretary to the Treasury Priti Patel stated: "The Government is demonstrating its long-term commitment to supporting the North Sea oil and gas industry.

"Our new package of measures is designed to reduce the tax burden on the industry, driving investment in the North Sea that will provide economic benefits to the UK for many years to come."

Scottish Energy Minister Fergus Ewing said: "Following the UK Government's admission that it has been 21 years since the oil and gas industry last received a tax reduction, the package of measures announced at the Autumn Statement is a first step to improving the fiscal regime for the industry.

"However, this announcement only goes a short way towards reversing the unexpected and damaging 12% increase in Supplementary Charge tax introduced by Danny Alexander at the 2011 Budget. They raised tax by 12% in 2011 and now cut by only 2%. To claim credit as they do on an overall tax hike of 10% will not impress many in the industry. They promise more cuts in future but offer no plans far less timescales. That is not good enough.

"It is encouraging to see that the UK Government has taken on board the recommendation from Scotland's Expert Commission on Oil and Gas in moving towards investment allowances based on capital costs rather than the physical characteristics of a field. Spreading this approach more widely should reduce the currently complex and confusing system which acts as a barrier, not an incentive, to investment. In driving forward these changes, it is essential that the UK Government engages with the industry, the new regulator and the Scottish Government to maintain momentum with these critical fiscal reforms.

"The UK Government has also committed to considering the wider economic benefits from oil and gas production rather than simply focusing on the short-term impact on revenue. Again, building on Scotland's Expert Commission recommendations, I strongly believe that this needs to be introduced as part of a fundamental shift in the way oil and gas policy is formulated, focusing on maximising the Total Value Added (TVA) generated by North Sea activity for the wider economy and society."

But Friends of the Earth's policy and campaigns director Craig Bennett said: "While the international community is trying to thrash out a plan in Lima to head off the threat of catastrophic climate change, the UK Government is trying to squeeze as much oil out of the North Sea as it can.

"This is environmental and economic illiteracy of the highest order.

"Ministers must end their obsession with dirty fossil fuels and build a clean economy for the future based on energy efficiency and the nation's huge renewable power resources."