Barclays says that a "technical breakdown" in the UK's clearing system forced it to borrow \ufffd1.6bn from the Bank of England.
It is the second time this month that the bank has tapped into the central bank's emergency credit line, sparking fears it is facing a cash crisis.
But the UK bank insisted it was "flush with liquidity".
At the end of every day, banks such as Barclays have to settle their trades through the market settlement system.
Typically, if borrowings are greater than their reserves at the end of the trading session, banks can borrow money from other banks to make up the difference.
Barclays explained that it was forced to tap into the Bank of England's emergency credit line because a technical glitch meant it discovered the shortfall in its finances too late in the day to borrow from another high street bank.
The move is very suspicious in the current situation. This is the second time the bank has had to get emergency loan money recently, and their structured debt manager resigned suddenly last month.
It could just be a coincidence, but really deserves investigation.
Jay