The Scottish Government has been asked whether its plan to siphon off money for a Norway-style oil fund will be funded by topslicing existing taxation or levying more taxes on the oil industry.
The SNP administration hopes to save a portion of its oil revenue in an independent Scotland for future generations, in a scheme inspired by Norway's lucrative oil fund.
Speaking during an oil debate in Holyrood, Labour energy spokeswoman Rhoda Grant said: "It is really unclear whether or not this will be topsliced from existing taxation, and if indeed the levels of taxation will remain comparable to the rest of the UK, or whether this will be a new tax levied on industry."
Oil revenues have contributed up to a fifth of Scotland's annual income (21.3%) over the last decade.
Scotland raised £8 billion from oil in 2010/11 compared with £39 million in Norway, according to analysis by the Scottish Parliament Information Centre (Spice).
Norwegians also paid £94 billion in other taxes from a population roughly the same size as Scotland, which gathered £45 million in tax.
Ms Grant added: "Companies need to be able to plan ahead and develop new fields and technologies, and this is a point stressed by Oil & Gas UK. It is, therefore, important that the Scottish Government is clear about what their regime for oil and gas will be should Scotland leave the UK.
"While they pursue their goal of independence, they have to ensure that during this campaign and the period of uncertainty that the industry has clarity to enable them to continue to develop. What might the fiscal regime for decommissioning be in an independent Scotland?
"Would decommissioning relief contracts entered into by the UK Government be honoured in Scotland if it were no longer part of the UK? Failure to answer these questions will cause instability and hinder development, and possibly lead to the early decommissioning of fields."
Energy minister Fergus Ewing said Scotland will honour its responsibilities in respect of decommissioning. "As far as taxation is concerned, we recognise that stability and predictability are absolutely key. The worst possible thing is to see any repetition of the tax hike that the industry faced, without any warning, in 2011 of an additional 12% supplementary petroleum tax. This did do considerable damage to undermine confidence in investors in oil in companies based throughout the world," he said.
