Not challenging enough? Standard & Poor's president moves on

Fresh from incurring the wrath of the US president by slashing the credit rating of the world's biggest economy, the president of Standard & Poor's is abruptly moving on to "new challenges".

The departure of Deven Sharma comes less than a month after S&P's unprecedented move to strip the US of its AAA credit score, citing the political wrangling over tackling its $14.3 trillion deficit.

Sharma's exit comes days after news of a US Justice department probe into whether S&P improperly rated dozens of toxic mortgage-backed bonds in the years leading up to the financial crisis in 2008, which sent parent company McGraw-Hill's shares tumbling last week.

S&P's downgrade of the US three weeks ago looks to have made the company plenty of new enemies in Washington.

The move sent shockwaves through global financial markets and was sharply criticised by the Obama administration, which said S&P's analysis was fundamentally flawed. Rival agencies have maintained their AAA ratings on the US.

Sharma joined the firm in 2006. He will be replaced as president by Douglas Peterson, chief operating officer of Citigroup's chief banking arm, Citibank.

Peterson takes over in September but S&P has said Sharma will stay on as an adviser until the end of the year.