World Wildlife Fund Scotland said ministers should be targeting renewable technologies instead of "squeezing every last drop of oil from the sea".
Norwegian firm Statoil has been cleared to start work in the Mariner heavy oil field, about 93 miles east of the Shetland Isles, which it says is the biggest new offshore development in the UK in more than a decade. The £4 billion project is set to create more than 700 jobs, including 200 onshore posts in Aberdeen.
WWF Scotland director Lang Banks said: "Instead of giving oil companies tax-breaks to help squeeze every last drop of oil and gas out from beneath our seas, Government should be taking steps to help prepare Scotland and the UK for a post-oil future."
Statoil expects to start production from Mariner in 2017 and the field is expected to produce for 30 years. The average production is estimated at 55,000 barrels of oil per day from 2017 to 2020.
Chief executive Helge Lundsaid: "The North Sea is a core area for Statoil and we look forward to taking a leading role in further developing also the UK part of this basin."
Robert Collier, chief executive of Aberdeen and Grampian Chamber of Com-merce, said: "Statoil's Mariner development is a signifi- cant investment, bringing even more high skill and high value jobs into the region."
A Scottish Government spokeswoman said: "We welcome this announcement, which will generate jobs and investment."