The SNP has been accused of "deceiving" voters in September's referendum after analysis suggested an independent Scotland would have received only a fifth of the party's oil revenue estimates.
The Financial Times reported that projections from the Office for Budget Responsibility (OBR) which take into account plummeting prices put oil revenues at £1.25 billion in 2016/17 - the first year of independence had Scotland voted Yes - instead of the £6.9 billion predicted by the Nationalists during the campaign.
Meanwhile oil giant Shell confirmed it is to sell its share in the Sean gas field in the southern North Sea.
First Minister Nicola Sturgeon said the Scottish Government is doing everything it could to help the industry as opposition parties called for urgent action to protect jobs.
Conservative leader Ruth Davidson said the country would have faced "financial meltdown" in the event of independence.
She said: "The SNP told the people of Scotland that the oil price would rise, it would stay high and there would be so much surplus revenue, Scotland could afford an oil fund for the future as well as finance all of the Scottish Government's day-to-day spending commitments as well.
"Expert after expert pointed out how fanciful this was - and yet Alex Salmond, Nicola Sturgeon and John Swinney insisted a new oil boom was on the way. It was nonsense then and it is nonsense now.
"It was the worst kind of deceit to try and bribe voters before the referendum and it is to Scotland's great credit that the majority voters saw through their fantasy economics.
"Now the oil price has crashed, their silence is deafening.
"It's time for them to acknowledge the deception they were trying to spread and to work to save the North Sea jobs now under threat from the hard realities of a volatile world oil market."
Liberal Democrat leader Willie Rennie said: "Imagine if Scotland had voted Yes in September. We would not only be facing the current jobs crisis but also a crisis in the Scottish Government's finances. The first days of creating a new nation would have been mayhem. As part of the UK we are able to protect the NHS and other public services and provide tax incentives to support jobs.
"But the referendum is done. The most pressing issue facing the North Sea oil industry and both of Scotland's governments is how to ensure the future viability of offshore production."
Labour repeated its call for the Government to make available its assessment of the long-term impact of falling oil prices on the North Sea oil industry, publish an updated oil and gas bulletin and order an inquiry into its pre-referendum predictions.
Lewis Macdonald, shadow business, energy and tourism minister and MSP for North East Scotland, said: "With experts saying it may be years before the price of oil recovers, it is urgent that the Scottish Government does everything it can to protect the jobs of thousands of people working in the oil industry.
"The SNP built an entire economic case for an independent Scotland on oil revenues of £6.9 billion. Those predictions lie in tatters today. Nationalist ministers must learn the lessons of the past so we can secure the future of such a vital industry."
The First Minister signalled her willingness to engage with a council summit on the difficulties facing the industry.
Jenny Laing, Labour leader of Aberdeen City Council, wants politicians, trade unions and industry bodies to come together to draw up a plan to save jobs in Scotland's oil capital.
Labour has pledged to send leader Jim Murphy while Scottish Secretary Alistair Carmichael MP and Lib Dem leader Mr Rennie have confirmed they will attend.
Ms Sturgeon said: "The Scottish Government will be fully involved in every effort to help the industry. I don't think we've yet received the invitation but when we do we'll respond positively to that.
"Separately to that, we'll be working pro-actively with the industry to make sure we're doing what we can but also that we're bringing people together to call on the UK Government to take the action that the industry really needs."
The First Minister added: "This is a difficult time for the oil industry. I think everybody hopes that it will be a temporary challenge to the oil industry but it does put a real onus on Government to work with the industry to help it through these difficult times.
"The Scottish Government will do everything we can around support for skills, for innovation, for training, and we're also calling on the UK Government, which holds the powers over tax on the industry, to deliver incentives to bring forward action that they have promised so that we're giving maximum support to the industry at a time when they need it."
A Shell spokeswoman said: "Shell can confirm that it has signed a Sales and Purchase Agreement with Oranje-Nassau Energie B.V. (ONE), for the sale of its 25% interest in the Sean field and some adjacent exploration areas. The deal is subject to partner and regulatory approvals, with completion expected in the first half of 2015.
"This deal shows that Shell is delivering its strategy to focus on areas where the company can add value in the UK Continental Shelf.
"Sean has entered a phase where it offers greater value to other companies than it does for Shell."
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