BHP and ExxonMobil have backed down on the planned sale of their ageing oil platforms in the Bass Strait.

Just 20 months after putting them on the market, the company has decided to keep the fields.

“After consideration of a range of options, we have currently decided to retain ownership and operation of these assets,” he said.

“We are committed to our Australian operations and ensuring the safe and reliable delivery of oil and gas to our customers.”

The fields include Australia's oldest and largest oil field, Kingfish A and B.

The 50:50 Gippsland Basin Joint Venture says it has also decided not to sell the Perch, Dolphin, Seahorse, Tawhine, Fortescue, West Kingfish, Halibut, Cobia, Mackerel, Blackback and Flounder fields.

Production at the offshore oil fields is in decline, so the companies are now expected to try to boost investment and increase production.

Oil prices have jumped by over 25 per cent since the company announced plans to sell the assets.