Barclays saw shares plunge to levels not seen for more than three years today amid renewed fears over the bank's vulnerability to the credit crunch.
The group's shares dived by 5%, extending the near-6% fall seen on Friday as speculation mounted over the impact on the bank of the tightening in credit markets.
The FTSE 100 Index continued to be dogged by uncertainty today, falling another 100 points after declines on Thursday and Friday.
Barclays came under further pressure after news the credit crunch had claimed yet another scalp, with the boss of US rival Citigroup quitting amid hefty losses and write-downs from exposure to crisis-hit US sub-prime mortgages.
Less than a week earlier Merrill Lynch chief executive Stan O'Neal was forced out following an eight billion US dollar write-down on losses in the sub-prime lending sector.
A downgrade from analysts at HSBC added to Barclays' woes, suggesting there may be more potential misery to come for the embattled banking sector.
A note from HSBC reportedly said share price falls do not yet price in the full extent of the possible fall-out from the credit squeeze.
Barclays has also been hit by rumours that the group had been forced to turn to the Bank of England for emergency funding.
The Bank of England confirmed that funds were not withdrawn from its standing facility on Friday, but the speculation fuelled growing concern that there is more misery to come for the group from the credit crisis.
Barclays declined to comment on its share price movement, referring only to last month's trading statement which said it expects its investment banking arm Barclays Capital to remain profitable for the remainder of the year.
Barclays has sought to reassure that there is no black hole in its finances, although it has yet to put a figure on the impact of the collapse of the US sub-prime mortgage market and subsequent credit problems.
It estimated in August that its likely maximum exposure to sub-prime-backed investment vehicles SIV-lites would likely be no more than £75 million. But the group is set to face calls to accurately reveal its total liabilities, with many looking to its November 27 trading update for further detail.
One banking analyst said it was investor nervousness that was driving Barclays' share price falls, given that the group's own directors were buying stock at the end of last week.
"Markets like this are characterised by fear and that's what we're seeing in the stock price movements," he added.
However, Barclays is not the only bank suffering losses on the London market, with NatWest parent Royal Bank of Scotland and mortgage specialist Alliance & Leicester also on the list of top share fallers on the FTSE 100 Index.
Banks have led sharp losses on the Footsie since the end of last week, with the blue chip index dropping nearly 300 points in the past three trading sessions.
Worries over the sector have added to concerns over the US housing market and economy, with inflation now also in focus as the cost of oil last week reached new all time record highs.