SNP's Alex Salmond has continually pledged that Scotland can go it alone with abundant oil revenues
Scottish Independence: Salmond's Bid to Keep the Pound and EU Membership is a 'Delusional Pipe Dream' Reuters

Investment bank Societe Generale has hit back at the Scottish Nationalist Party's claims that an independent Scotland would be able to keep the pound if voters chose to break the 307-year old union with England.

Despite Scotland's First Minister Alex Salmond promising citizens that an independent country would retain the pound and its European Union membership, the country would have a tough time keeping either and would have to work harder in controlling its debt, according to the bank's research team.

"To persuade the UK to let it continue to use the pound as its currency in a formal currency union looks like a pipedream," said Brian Hilliard, chief UK economist at Societe Generale.

"That would mean that Scotland would then have to create its own currency with all that entails - a new central bank, lender of last resort facilities, [and] build-up of foreign exchange reserves. The yes camp is deluding itself if it believes it can both retain the pound but also become master of its own fiscal affairs.

"The 'Yes' camp seems convinced that it could easily negotiate re-entry into the European Union as a separate state without committing to join the euro. This seems very unlikely."

Scottish people will vote in an independence referendum on 18 September, 2014, and will be asked the straight "yes/no" question: "Should Scotland be an independent country?"

The referendum period started on 30 May.

During the 5 August televised debate between SNP's Salmond and former Chancellor Alastair Darling, the leaders of the Yes and No campaigns tried to make the case for voting for or against independence.

Salmond has consistently pledged to voters that an independent Scotland would keep the Sterling, its EU membership, and would be financially stable to go it alone because it has a glut of North Sea oil to buoy up its balance sheet.

However, Hilliard warned that the pro-independence camp is not acknowledging to the public about how Salmond's jewel in his crown – North Sea oil – is drying up and the country will not rake in as much as he is claiming.

"North Sea oil is no longer the crock of gold the Scots imagine it to be", said Hilliard, adding that the pro-independence campaign is exaggerating how much money the country would make in tax receipts.

The Office for National Statistics (ONS) revealed that the rate of profit at oil and gas exploration and extraction companies tanked to 27.6% in the first quarter of 2014 - its lowest level since the second quarter of 2009.

Meanwhile, the Organisation of Petroleum Exporting Countries (Opec) revealed that the average oil output in 2013 from the North Sea registered its lowest level since 1977.