Rating agencies Moody's and Standard and Poor's have lowered their outlook on Barclays from stable to negative amid the bank rate-rigging scandal.

Moody's said shareholder and political pressure was creating uncertainty about the bank's future.

S&P said the emergence of "weak business practices" had hit the company's prospects.

The move comes a day after ex-Barclays chief executive Bob Diamond told MPs the rate fixing was "reprehensible".

MPs will vote later on whether to have a judge-led inquiry over the scandal, favoured by the opposition, or a parliamentary one, favoured by ministers.

Moody's said pressure on the bank could force it to move away from investment banking.

"Although this could have potentially positive implications over the longer term, the uncertainty surrounding such a change in direction is credit negative in the short term," the agency said.

It added that Barclays may find it difficult to replace Mr Diamond, chief operating officer Jerry del Missier, and chairman Marcus Agius, all of whom resigned this week. Mr Agius is staying on at the bank to oversee finding a replacement for Mr Diamond, but will step down once someone has been found.

S&P said "weak compliance" and "current management flux" had knocked the company's outlook.