Standard & Poor's has cut the credit ratings of Barclays, Credit Suisse and Deutsche Bank due to "uncertain market conditions".
The European Commission has accused 13 banks, including Barclays, HSBC and the Royal Bank of Scotland, of colluding to hamper competition in the credit derivatives market.
UK banks need to raise billions more in capital to cover their risks, the regulator has said.
Barclays' wealth division has closed its discretionary fund management service to advised clients with less than £250,000 of investable assets.
Barclays has been dragged into the scandal surrounding Liberty Reserve, a US cash-transfer business accused of running the biggest money-laundering operation in American history.
Barclays' Q1 adjusted pre-tax profit has dropped 25% to £1.8bn after the bank took a £500m hit over its restructuring programme.
Bond managers have been steadily increasing the use of credit default swaps (CDS) in their portfolios as liquidity issues which emerged in the corporate bond space last year continue to plague the sector.
Barclays' investment banking chief Rich Ricci and wealth management head Tom Kalaris are to retire as the company restructures its senior management team.
Ashok Vaswani, chief executive of retail and business at Barclays, has admitted that 2012 was a "very difficult year" for the bank, and said the decision to release details of staff's £38.5m bonus details on Budget day was a "mistake" but claimed it was...
Barclays has been named as the Financial Conduct Authority's (FCA) most complained about firm for the second half of last year.