London - Shares in Edinburgh-based Lloyds Banking Group and Royal Bank of Scotland fell on Monday after supporters of Scottish independence took their first opinion poll lead since the referendum campaign began.
Lloyds' shares were down 2.5% by 08:45 GMT and Royal Bank of Scotland's down 2.3%. Shares in TSB, which does a quarter of its mortgage lending in Scotland and is majority-owned by Lloyds, were down 2.8%.
Scotland will vote on September 18 whether to stay in the United Kingdom.
Economists have questioned whether an independent Scotland would be able to host such large banks. Banking industry sources told Reuters last week that Lloyds is considering moving its registered offices to London if Scots vote for independence. RBS is examining its options.
The two banks have warned that Scottish independence would present a significant risk to their businesses, impacting their funding, tax and compliance costs.
Analysts at Credit Suisse said that a vote for independence would result in complex legal issues and additional costs for both Lloyds and RBS, whose registered offices are in Edinburgh.
They also said a "yes" vote could complicate the privatisation of Lloyds and RBS. The government pumped a combined $106.7bn into the banks to keep them afloat during the 2008 financial crisis.
The British government holds a 25% stake in Lloyds, having sold 13.5% of the shares over the past year and had hoped to sell more this month if Scots voted against independence. Those plans will be put on hold if there is a "yes" vote.
The government also holds an 81 percent stake in RBS whose shares are trading below the price it paid for them.