The Bank of England was forced on Friday night to confirm that it was secretly researching the financial impact of a possible decision by Britain to leave the EU, after it mistakenly emailed a journalist with the details.
The confidential email, mis-sent to the Guardian newspaper, is reported to include details of the study, dubbed "Project Bookend". It also stated that the press and most staff at the BoE should be kept in the dark about the work under way.
The decision by the central bank comes only weeks after the Conservative party secured a majority in the UK general election, paving the way for a referendum by 2017 on British membership of the EU.
On Friday, David Cameron began discussing with European partners how to renegotiate the position of the UK in the EU in advance of the referendum.
The BoE issued a statement responding to the revelation, saying it was entitled as a regulator to conduct studies over possible financial shocks that could hit the UK.