Independent Scotland would lose UK's AAA rating, warns Citigroup

The bank’s verdict comes despite claims by Alex Salmond, the Scottish First Minister, over the impact on the Westminster government coffers from the loss of North Sea oil revenues.

“The direct effects of Scottish independence would probably be to marginally cut the fiscal deficit of the rest of the UK, since Scotland’s fiscal deficit slightly exceeds the UK level,” said Citi’s team of analysts in the 20-page report.

Although Citi’s view is that it is highly unlikely that Scotland will vote to split from the UK, the bank warned that “the possibility of Scottish independence has generated political uncertainty within the UK, and confusion abroad”.

A spokesman for the Scottish government did not respond to a request for comment.

Meanwhile, it emerged on Friday that Alliance Trust, the historic Dundee investment firm, has set up two new subsidiary companies in England to prepare for the possibility of an independent Scotland.

The 126-year-old investment trust has become the latest major listed company to warn about the “uncertainty” created by the independence referendum and the potential impact of Scotland’s no longer using the pound or staying in the European Union.

Alliance, which manages and administers more than £10bn, said that it had registered two new companies, Alliance Trust Investments England and Alliance Trust Savings England, to ease customers’ concerns over what would happen in the event of a “yes” vote on September 18.

Katherine Garrett-Cox, chief executive of Alliance, insisted the move was not politically motivated and did not herald the start of a “wholesale shift” of the business “at this point”.

But she said it was “critical” that the company was able to ensure continuity and protection for customers, about 80pc of whom live outside Scotland. The trust estimates that two-thirds of its shareholders are also not based north of the border. Ms Garrett-Cox said customers had contacted the trust over the past few months to highlight their fears, in particular over the future taxation of savings and pension plans should Scotland leave the union.

Alliance also stressed that any changes to financial-services regulation, currency and EU membership would affect both the business itself and customers.

However, Ms Garrett-Cox said she would not be warning the Westminster government over the possible fallout from a referendum on the UK quitting the EU.

“That is not our current intention because from our perspective, that is not an issue our customers are raising with us today,” Ms Garrett-Cox said.

She added: “We are very specifically not making a political statement here. What we are doing is putting our customers absolutely front and centre. And unsurprisingly, I would say over the last weeks and months, we have had increasing communication with them around some of these concerns.”

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