The credit ratings of Scottish insurers would be at risk if the country leaves the UK, Standard & Poor’s has warned.

The agency, which rates Edinburgh-based Standard Life, Scottish Equitable and Scottish Widows, said on Friday there was “potential for negative ratings impact” if Scotland votes for independence next month. S&P’s concerns include regulation, taxation and the possibility that an independent Scotland could have a lower sovereign debt rating.

Insurers employ an estimated 26,000 people in Scotland – almost a third of the country’s wider financial services sector, which accounts for about 13 per cent of its economic output.

Scotland also plays a crucial role in the wider UK sector and is the second most important location for life and pension companies outside London and the southeast.

The country accounts for an estimated $12bn of life and pension premiums and about $6bn in non-life premiums.

Large UK-wide insurers including Aviva and Prudential have sizeable operations in the country.

Standard Life and Scottish Equitable are both rated A plus by S&P. Both companies have made “contingency plans ” for a Yes vote and Standard Life has registered legal entities south of the border.

S&P made clear that it also foresaw risks to insurers’ perceived creditworthiness even if the country stays in the union.

The main UK political parties have pledged to give the Scottish parliament more powers, which could also lead to tax and regulatory changes.

However, Mark Nicholson, the lead author of the S&P report said these risks were “much smaller” than full blown independence.

The agency said: “Were Scotland to become fully independent, it’s likely that life and pension products sold by insurers based in Scotland would no longer qualify for favourable tax treatment for policyholders in the UK.”

Mr Nicholson raised particular concerns about the currency that an independent Scotland would use.

He highlighted that insurers hold a large proportion of government bonds in assets used to back the policies they write.

Standard & Poor’s has previously warned that Scotland would struggle to match the UK’s triple A credit rating if it failed to negotiate a currency union with London or the eurozone.

However, it has also highlighted potential strengths of an independent Scottish economy.

S&P did not name any specific insurance companies in its report.

The agency said the referendum outcome was unlikely to have an immediate effect on insurance companies given that Scotland would not become independent, or its devolved parliament be given more powers, until at least 2016.

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