By Josie Cox 

The British pound plummeted to a near nine-month low Monday, while Scotland-focused stocks also fell, whacked by a poll over the weekend showing that the number of those favoring Scottish independence had eclipsed those opposing a split for the first time since the referendum campaign began.

Sterling dropped almost 0.9% in early trade to $1.6153, marking its lowest level since November last year, while the euro gained 0.8% against the pound to GBP0.8015. Citigroup said in a note that sterling could now easily slump to $1.56 in the event of a 'yes' vote, echoing earlier remarks from strategists last week.

In equity markets Monday, Royal Bank of Scotland Group PLC shares fell 2.8%, making the lender one of the biggest losers on London's FTSE 100 index, followed closely by Scottish domiciled names such as Standard Life PLC and SSE PLC. The broader index edged 0.2% lower, having last week hit a 14-year intraday high.

The latest YouGov poll released Saturday showed 47% of those surveyed were now likely to vote "yes" to independence, while 45% would likely say "no." The rest of the 1,084 voters polled Sept. 2-5 said they were undecided or wouldn't vote.

Paul Donovan, an economist at UBS, said that even if the pro-unionists took the lead on September 18, the latest figures raise the risk of what he dubs a "Québécois scenario"--a narrow rejection of independence that leaves open a risk of a further vote.

"We believe this would have implications for banking, gilts, direct investment into Scotland--from overseas and the rest of the United Kingdom--and sterling," he said.

Already last week, the currency came under severe pressure as polls showed a narrowing of the two camps. Gilts and equities underperformed moderately too, while implied volatility rose.

On Monday, the yield on the U.K.'s 10-year Gilt contract was at 2.490%, around 0.02% higher on the day. Yields rise as bond prices fall.

Barclays currency strategists pointed out that derivatives that protect users from sharp shifts in sterling are increasingly in demand.

"The abruptness of the shift in one survey should be viewed with caution, but nonetheless reinforces our long-held view that Scotland's independence referendum is a serious event risk, not a tail risk," they wrote in a note.

Monday marks a fifth daily decline for a currency that has fallen over 5% from a six-year high in July--and 2.1% for the year--as investors start to worry about issues such as Scotland's use of the pound or banking-regulation in the case of a split from the rest of the U.K.

Scotland's nationalist party says Scotland would continue using sterling, but all three main political parties in London and treasury officials oppose this, saying it would expose British taxpayers to financial risks from a country over which they have no control.

Scotland's membership in the European Union would also come under question, as it now belongs as part of the U.K.

Rebecca Howard and Anjani Trivedi contributed to this article.

Write to Josie Cox at josie.cox@wsj.com

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