The North Sea could still contain more than £1 trillion-worth of oil and gas, energy minister Fergus Ewing has said.

Mr Ewing told MSPs that with "significant unharvested reserves" it is possible that as many as 24 billion barrels can still be extracted.

He spoke out on the issue during a debate on oil and gas, a month after energy firm BP announced a second phase of development at the giant Clair field, west of the Shetland Islands.

Mr Ewing said around 39 billion barrels have been extracted from the North Sea since large-scale production in the 1970s.

"Production levels may have peaked in 1999 but the story does not end there, far from it," he said.

"Here we are 40 years after oil and gas pioneers in the North Sea first started to pump Scotland's oil, and still the North Sea continues to produce 900 million barrels every year. And the story continues with significant unharvested reserves remaining in the North Sea."

He told MSPs experts had forecast oil and gas production can continue until at least the 2040s, adding that industry body Oil and Gas UK has estimated that between 15 and 24 billion barrels remain.

"This suggests between 30% and 40% of total oil and gas reserves by volume have still to be extracted," Mr Ewing said.

"At current prices these reserves could have a wholesale value in excess of £1 trillion. Given this extraordinary potential it is therefore imperative that the recovery of these reserves is maximised."

He continued: "It is clear there remain considerable opportunities in the North Sea and that the industry will remain an important part of Scottish and UK economies for many decades to come."