Shares in BP were down on the FTSE 100 in afternoon trading after the energy giant said it would be selling its interests in the Wytch Farm onshore oilfield in Dorset and its operated gas fields in the Southern North Sea.
BP said that staff at the installations would most likely be retained by the buyers of the assets.
The company said it was divesting itself of the assets so that it could concentrate on other assets in more northern areas of the North Sea, West of Shetland and Norway.
While BP did not name any potential buyers the group said it hoped to have completed the sale by the end of 2011.
Trevor Garlick, Regional President, BP North Sea, said, "The North Sea is a significant business for BP and we are currently investing here at the highest level for more than ten years, with four major new field development projects underway in the UK and two in Norway. The assets we intend to divest are of high value but find it difficult to compete for capital and resource within our North Sea portfolio. We believe they will attract earlier investment and be of greater value to a new buyer.
"Ensuring continued safe operation of these assets will continue to be our priority as we seek potential purchasers and support our staff through the transition process which will follow."
By 14:00 shares in BP were down 0.71 per cent on the FTSE 100 to 488.05 pence per share.