The UK government was forced to rule out letting failed bank Northern Rock wind down because poor IT systems would have left depositors waiting for their money, risking another major run.
The revelation comes in a report by the National Audit Office (NAO) on the government's handling of the failed bank, which was nationalised in February 2008.
The report says that in September 2007 the Treasury considered stopping Northern Rock from taking deposits and writing new mortgages and beginning a process of winding down the company.
However "inadequate IT systems at Northern Rock meant that depositors would have had to wait for their money".
The firm operated a manual account closure process and estimated that it would have taken up to 10 to 12 weeks to repay depositors, with a likely error rate of 25%.
This would have risked another major run and potential hardship for those reliant on access to their funds, says the report, forcing the government to rule out an immediate wind-down on "practical grounds".
The report says work on updating the technology was then begun to enable quicker repayment of depositors if needed at a later stage.