A secret Bank of England project to examine the economic risks of the UK quitting the EU in the referendum has been revealed after an email was accidentally sent to a journalist.
The existence of the confidential work, code-named Project Bookend, came to light as David Cameron met with other European leaders in Riga, Latvia, to start talks on reform "in earnest".
The Prime Minister has promised an in/out vote on Britain's membership of the 28-nation group by the end of 2017, based on a new deal with Brussels.
Businesses have already warned over the dangers of a so-called Brexit, with the Confederation of British Industry pressing to remain part of a reformed EU.
Aerospace giant Airbus recently became the latest company to warn it would reconsider investing in the UK were to leave.
And it has now emerged work is being carried out in Threadneedle Street to assess the impact of a potential UK exit, after an email was inadvertently sent to The Guardian newspaper by the Bank's head of press, Jeremy Harrison.
The newspaper said it revealed the task force would be made up of a select group of senior staff, headed by Sir Jon Cunliffe, who as deputy director for financial stability is responsible for monitoring the threat of another market crash.
Following the email blunder, the Bank said in a statement: "Today, information related to planned confidential Bank work on the potential implications of a renegotiation and national referendum on the UK's membership of the European Union made its way into the public domain, due to an internal email sent inadvertently to an external party.
"It should not come as a surprise that the Bank is undertaking such work about a stated government policy.
"There are a range of economic and financial issues that arise in the context of the renegotiation and national referendum.
"It is one of the Bank's responsibilities to assess those that relate to its objectives.
"It is not sensible to talk about this work publicly, in advance.
"But as with work done prior to the Scottish referendum, we will disclose the details of such work at the appropriate time.
"While it is unfortunate that this information has entered the public domain in this way, the Bank will maintain this approach."
