Pro-union supporters take part in a demonstration in Glasgow after Scotland voted to remain part of the U.K. in a referendum Sept 18. The Bank of England disclosed Friday that it planned to dish out emergency cash to banks in difficulty had Scotland voted for independence. European Pressphoto Agency

LONDON—The Bank of England planned to dole out emergency cash to banks in difficulty had Scotland voted for independence last month, the central bank said Friday, in a rare disclosure of officials’ contingency plans in the event of a threat to the stability of the U.K. financial system.

Officials on the BOE’s Financial Policy Committee were briefed in June, July and August about the central bank’s preparations to manage any financial disruption had Scots voted to secede Sept. 18.

The plans were published Friday in the record of the panel’s Sept. 26 meeting after officials agreed they no longer needed to be kept secret. Scots voted to stay in the U.K. by a margin of 55% to 45%, in a referendum that electrified Scottish society and caught the attention of the world.

The disclosures highlight the depth of central-bank officials’ concerns over the potential consequences of a vote for independence. They also detail the step-by-step plan the BOE drew up to maintain stability had the ballot gone the other way.

Of particular concern to officials was the uncertainty over an independent Scotland’s currency arrangements, which could have hurt Scottish financial institutions. Before the vote, London had ruled out a sterling currency union with the new state, casting doubt on whether Scotland could keep using the pound. Depositors fearful of losing their sterling savings could have pulled their cash out of banks and insurers and creditors could have stopped providing funds, the BOE said. Financial firms themselves may have sought to get rid of Scottish assets.

“It was possible that the prospect of that risk materializing in the future could have threatened financial stability in the present,” the Financial Policy Committee concluded.

In response, the BOE planned first to reassure Scottish businesses and households that it remained responsible for preserving financial stability in both Scotland and the U.K. until such time as the new state formally seceded.

The central bank judged that had Scottish institutions moved their registered domicile to England, a degree of financial disruption could have been avoided. But it also planned to offer the banking system emergency cash in unscheduled sterling auctions in the two weeks immediately following the vote, as well as dishing out loans to individual banks in urgent need of funding.

“A key element of the bank’s contingency planning work concerned the potential provision of liquidity support to individual institutions,” according to FPC records. The central bank also put plans in place to meet an anticipated surge in demand for Bank of England bank notes to replace notes issued by Scottish banks.

During those summer meetings, the FPC “emphasized the importance of readiness of the bank, in conjunction with [the U.K. treasury] to take steps rapidly in the event of a ‘yes’ vote.”

The record of the FPC’s Sept. 26 meeting also shows officials are increasingly worried more broadly about risk-taking in the financial system. Officials noted lending standards were more lax in some markets and underscored earlier concerns about a shortage of liquidity in others.

The panel warned financial firms may not be sufficiently prepared to withstand unexpected losses, a sign that officials may consider fresh action to bolster the financial system at meetings later this year.

Write to Jason Douglas at jason.douglas@wsj.com