Ineos has signed a $1bn (£770m) deal to make it the biggest private enterprise in the North Sea.

The British firm has bought up Dong Energy's interests across the Danish, Norwegian and UK sectors.

The takeover will reportedly add about 100,000 barrels of oil to Ineos' total daily production.

Opponents have accused Ineos - which co-owns Scotland's only crude oil refinery and plans to buy the UK's biggest oil pipeline - of already having too much control over the North Sea.

Ineos chairman Jim Ratcliffe said: "Dong Energy's oil and gas business is a natural fit as we continue to grow our upstream activities.

"We are pleased to acquire this competitive, well-run business, with its highly successful and experienced team, a strong portfolio of long-life assets and a very good mix of existing production and developments across the North Sea."

No jobs are expected to be lost as a result of the takeover and all 440 Dong Energy staff will transfer to Ineos.