and Pitt battles to save his job

The news comes after Pitt battled through months of pressure on the SEC following the catastrophic failures of Enron and WorldCom and after recent political infighting over his choice of leader for the US' new accountancy regulator.

President George Bush has accepted the resignation, (the post is a White House appointment) but it comes just days after he offered renewed backing for Pitt.

Pitt was in Brussels just two weeks ago to convince politicians and accountants of the benefits of the controversial Sarbanes-Oxley Act on corporate governance. The legislation has been criticised heavily in the UK for its cross-borders effects and UK ministers were hoping to win important concessions from the SEC chief. It is unclear whether those plans will be undermined by the appointment of a replacement for Pitt.

However, it was Pitt's recent efforts to appoint former CIA chief William Webster to head the Public Oversight Board, a new US accountancy watchdog, that proved most damaging. Just days after the appointment Pitt was forced to launch an investigation when it was revealed that Webster had been audit committee chairman of US Technology - a company caught up in a fraud scandal.

The investigation looked from the outside as if Pitt was probing his own appointment.

This came after Pitt had fought off fierce political opposition to Webster's appointment.

in a letter to the White House Pitt said: 'Rather than be a burden to you or the agency, I feel it is in everyone's best interest if I step aside now, to allow the agency to continue the important efforts we have started.'