Energy giant Shell has published the details of how it intends to decommission the Brent oil field.

Shell intends to remove upper section of the 30,000-tonne steel structure which supports the Brent Alpha platform, along with the upper sections of all four Brent facilities.

However, it wants to leave parts of the structures in place, including the concrete and steel feet of Brent Alpha.

Environmental groups have raised concerns about the plan, which will be the first major North Sea decommissioning project.

A 60-day consultation on the plans was launched on Wednesday.

Brent decommissioning asset manager Duncan Manning said: "After an extensive and in-depth study period, the submission of Shell's Brent decommissioning programme marks another important milestone in the history of the Brent oil and gas field.

"Shell has undertaken thorough analysis, extensive scientific research and detailed consultation with over 180 stakeholder organisations over the past ten years.

"Working within the tightly defined regulatory process, we believe that our recommendations are safe, technically achievable, environmentally sound and financially responsible.

"Shell encourages all those with an interest in the decommissioning of the Brent field to review, reflect on and respond to this consultation document."

WWF Scotland director Lang Banks said the environmental charity would "carefully examine" Shell's plans.

"The rules already allow for companies to seek permission to leave some material behind - such as the massive concrete legs - where moving it would pose an unacceptable risk to staff or the environment. We accept this principle.

"If the oil within the cells and some of the drill cuttings occur above limits that internationally agreed standards recommend they should be removed in order to prevent damage to the environment.

"The main thing preventing this from being done in this particular case is the cost. Shell should do the right thing and remove these potentially polluting materials."

"If done right, it could open the door for this country to lead a new multi-billion pound, global decommissioning industry that could create thousands of jobs as we continue our transition away from fossil fuels," he added.

First Minister Nicola Sturgeon visited Aberdeen on Wednesday to announce plans to create a £5m decommissioning fund for the oil and gas industry.

The North Sea decommissioning sector will worth more than £17bn over the next decade, according to industry body Oil and Gas UK.

More than 100 platforms will be completely or partially removed, with around 1800 wells scheduled to be plugged and 4600 miles of pipeline to be decommissioned. The market was reportedly worth around £2bn in 2015.

Ms Sturgeon said: "With up to 20 billion barrels of oil and gas remaining, the Scottish Government's top priority remains working with industry and stakeholders to maximise economic recovery from the North Sea.

"The new £5m fund also recognises that decommissioning is an emerging, but growing, activity in the North Sea, with £17.6bn expected to be spent in the North Sea over the next decade."

"News today that Shell plans to apply to begin decommissioning its Brent oil field underlines the importance of planning for decommissioning," she added.

"The fund builds on our Programme for Government commitment to identify investment opportunities, with a view to improving capacity at Scottish ports, increasing the economic return to Scotland from a variety of removal, disposal and dismantling activities."

Scottish Enterprise director Adrian Gillespie said: "While the focus should remain on maximising recovery, Scotland has the ambition and potential to position itself at the forefront of the global decommissioning industry."

The Brent oil field was the scene of the "Battle of Brent Spar", when Greenpeace campaigners occupied a decommissioned oil storage buoy Shell wanted to sink to the seabed.

They remained aboard the Brent Spar for almost a month in April and May 1995 before being evicted.

The buoy was later towed to Norway, where it was dismantled and used to build a quay in the village of Mekjarvik.