Prominent Tory MP and veteran eurosceptic Sir Bill Cash suggested the First Minister will come under the challenge from the UK Government over the vital revenue source’s ownership.
Ms Sturgeon has pinned her independence hopes on being able to secure sole ownership of the oil fields, which sit in the United Kingdom’s territorial waters, to underpin the Scottish economy.
Despite continuous warnings her economy has faltered, partly due to declining oil reserves, she maintains Scotland will be able to survive outside of the UK.
However, Sir Bill has launched his own attack on her referendum hopes, insisting she won’t be able to take the oil fields with her.
Sir Bill Cash suggested Nicola Sturgeon may have a battle on her hands for North Sea oil
North Sea oil is in significant decline
Sir Bill Cash
Speaking to Express.co.uk, the Tory MP said: “North Sea oil is in significant decline and it’s not producing the revenues.
“Even supposing they can get their hands on North Sea oil because there is an issue about territorial waters, which doesn’t seem to get discussed – they belong to the United Kingdom.”
The SNP argued during its failed independence campaign in 2014 that it could maintain its economy through the production of oil in the region.
But dwindling prices – from more than $100 (£80) in April 2014 to just $53 (£42) in December 2016 – has made the argument less palatable.
Figures last week revealed the economy north of the border has gone into reverse as the oil industry struggles.
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Addressing an audience in Glasgow on Tuesday, Ms Sturgeon reinforced her ambitions to hold the second referendum between Autumn next week and spring 2019.
Sir Bill insisted the Scottish people were unlikely to back Ms Sturgeon on her “unrealistic” calls for independence.
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The MP for Stone added: “There are so many reasons not to support Ms Sturgeon and I believe the Scottish people are incredibly sound and sensible when it comes to the crunch.
“They will be looking at all of this, and that is why the opinion polls are turning Nicola Sturgeon’s objectives.
“She is pitching a case which is unrealistic, and ultimately I believe the Scottish people will react against it and they are doing so already.”