The figure in a document outlining the industry’s prospects in an independent Scotland should have referred to UK-wide jobs and not Scottish jobs, Mr Swinney said.
The paper was published on July 23 and was amended three days later.
Mr Swinney has now acknowledged the error in a written response to Conservative finance spokesman Gavin Brown.
The minister said: “This was a result of an incorrect interpretation of data presented by Lloyds Banking Group by Scottish Government officials in the original published version of Maximising the Return from Oil and Gas in an Independent Scotland.
“The Scottish Government report was subsequently updated on the 26 July 2013 and it now states that: ‘Lloyds Banking Group forecast in March 2013 that future growth in the sector will create 34,000 jobs in the industry and related businesses across the UK over the next two years, with all areas of Scotland expected to benefit’.”
Opposition parties have accused the Government of trying to pretend the figure applied to Scotland alone and then quietly sneaking out a correction.
Mr Brown said: “On many occasions the Scottish Government has put its own unusual interpretation on figures and tried to paint it as reality.
“This time it used a UK figure and pretended it was a Scottish statistic, then blamed Lloyds for the mistake. However, it turns out the error was the Scottish Government’s and I’m glad that has now been clarified in black and white.
“It’s also concerning to note the Scottish Government doesn’t appear to have an estimate of the number of jobs that will be created in the oil and gas industry in future years. Given the separation argument relies heavily on the sector, this leaves a substantial gap; something that has to be addressed as soon as possible.”
Liberal Democrat leader Willie Rennie said: “I am sure there are a few red faces in government offices just now.
“What is more concerning is the fact that it seems ministers tried to correct the record without letting anyone know what they were up to. This was a basic factual mistake that should have been acknowledged and corrected in the full glare of the public eye. Instead they tried to sneak out a correction without fanfare while parliament was in recess.”
A Scottish Government spokeswoman said: “The projection of 34,000 new jobs was contained in a Lloyds briefing presented to the Scottish Parliament, which also indicated that all parts of Scotland are likely to benefit. The purpose of this section of our report was simply to highlight the substantial employment prospects for this thriving sector which is undoubtedly the case.
“Last month Lloyds confirmed that the projection was for across the UK. We made clear to media then that we would amend our paper to reflect that and reference it accordingly.
“The North Sea sector plans to invest almost £100 billion in future years, and the industry currently supports around 200,000 jobs in Scotland. With almost all oil production and more than half of gas production around these islands expected to take place in Scottish waters over the next three decades, clearly it will continue to create significant employment opportunities in Scotland for many years to come.”