Royal Bank of Scotland, which has been based in Scotland since 1727, has said there are a number of "material uncertainties" arising from the Scottish referendum vote that could force its relocation to England.
A statement said the "uncertainties" could have a bearing on the Bank's credit ratings, and the fiscal, monetary, legal and regulatory landscape, adding:
For this reason, RBS has undertaken contingency planning for the possible business implications of a Yes vote.
RBS believes that this is the responsible and prudent thing to do and something that its customers, staff and shareholders would expect it to do.
RBS said any move to re-domicile the Bank's holding company and its main operating entity should have no impact on everyday banking services, while it would retain a significant level of its operations and employment in Scotland.
Standard Life has also advised investors it is "planning for new regulated companies in England to which we could transfer parts of our business if there was a need to do so".
Royal Bank of Scotland has confirmed it plans to move its holding company to England if Scotland votes for independence in next week's referendum.
The Treasury said last night that officials from RBS had told them the bank was ready to follow Lloyds Banking Group with plans to relocate to London in the event of a majority Yes vote next Thursday.
Shares in Scotland-based financial institutions Royal Bank of Scotland, Lloyds Banking Group and Standard Life fell by more than 2% in the wake of the latest opinion poll.
Perth-based energy supplier SSE was also fell.
Edinburgh-based Standard Life, which has been based in Scotland for 189 years, recently complained that it was still in the dark over "material issues" surrounding independence.
The Financial Services Authority, the FCA's predecessor, raised concerns in November 2011 about branch and telephone sales at RBS and NatWest but it was almost a year later before the firms started to take steps to put things right.
The firms made assurances to the FSA in July 2012 that the necessary changes were underway to address the regulator's concerns, but the FCA said this "failed to happen".
Where we raise concerns with firms we expect them to take effective action to resolve them without delay. This simply failed to happen in this case.
Taking out a mortgage is one of the most important financial decisions we can make. Poor advice could cost someone their home so it's vital that the advice process is fit for purpose. Both firms failed to ensure that their customers were getting the best advice for them.
The Royal Bank of Scotland will contact 30,000 mortgage customers who may be concerned about advice they were given by the state-backed bank after the Financial Conduct Authority found "serious failings" in its mortgage advice to consumers.
The City regulator said that only two of 164 sales made by the state-backed bank between June 2011 and March 2013 were considered to meet the standard required overall in a sales process.
It found RBS and its retail arm NatWest failed to consider the full extent of a customer's budget when making a recommendation, while staff did not advise customers what mortgage term was appropriate for them.
The regulator said there was no evidence that there was widespread detriment to customers, although RBS and NatWest will contact 30,000 consumers so they can raise any concerns they have about the advice they received.
RBS said that in response to the regulator's findings at the end of 2012, it overhauled its mortgage sales process and re-trained all mortgage advisers.
Royal Bank of Scotland has been fined £14.5 million by the City regulator for failing to ensure that advice given to mortgage customers was suitable.
Profits at taxpayer-backed RBS have risen significantly in the first half of the year.
The bank said its preliminary results were "significantly stronger than the marked has been expecting", with an operating profit of £2.6bn compared to £708m in the first half of 2013.
However chief executive Ross McEwan issued a note of caution, saying there would still be "bumps in the road ahead" as the bank deals with various "legacy issues", such as the mis-selling of Payment Protection Insurance.
Along with the good news on profits, RBS also announced it had set aside an extra £250m to cover fines for mis-selling PPI and interest rate swap products.
British taxpayers risk losing their entire £45 billion stake in Royal Bank of Scotland (RBS) which is in grave danger of failing within 10 years, according to an explosive new book.
According to the Independent on Sunday, a new study of the bank, which brought the UK to the brink of financial ruin, reveals RBS still has a £100bn “black hole” in its finances due to “five broad areas of alleged criminality and wrongdoing”.
Financial journalist Ian Fraser, who wrote Shredded: Inside RBS, The Bank That Broke Britain, said: "The result has been that, at the time of writing, RBS is probably a worse bank than it was under Fred Goodwin.
“If the right moves are now made, RBS could become a great bank again. If they’re not, I doubt it will even exist in 10 years’ time".
Shares climbed an extra £2.5 billion adding to the value of Royal Bank of Scotland today after it said quarterly profits had doubled.
RBS, which is 80% owned by the taxpayer, said profits before tax had risen to £1.64 billion from £826 million in the same period last year, prompting shares to rise by 13% after news broke this morning.
Shares settled at 9% - despite a warning from RBS chief executive Ross McEwan that there were still "plenty of issues from the past to reckon with".
Mr McEwan said the latest figures showed the "great job" it could achieve while in a "steady state.
After the announcement of a pre-tax profit of £1.64 billion for Royal Bank of Scotland, Chief Executive Ross McEwan has said that his bank "still has a lot of work to do."
In a statement he said: "We still have a lot of work to do and plenty of issues from the past to reckon with.
"Everyone at RBS is focused squarely on doing everything we can to earn the trust of our customers and in the process change the banking sector for the benefit of the UK.”