President Bush has defended himself against allegations that he was personally involved in business practices that are at the heart of the scandal engulfing corporate America.

At a news conference in the White House, Mr Bush denounced criticism of his role as oil company director before he entered the political arena as "old style politics".

He was speaking after former senior executives of WorldCom refused to testify at a congressional hearing on accounting fraud at the company.

People are going to attack me based on Harken, that's nothing new

George W Bush

He looked ahead to a speech he is due to make in New York on Tuesday, in which he will give his considered view of what needs to be done to restore investor confidence.

He vowed to "vigorously pursue" executives who broke the law in an effort to restore people's confidence in American business.

But he began by urging Congress to act quickly to pass legislation providing funds for homeland security and the military campaign against terrorism.

"Further delays are intolerable," he said. "Congress must act."

Suspicions

Mr Bush is at pains to stress his personal investment in fighting corporate dirty dealings, not least because he is not alone in facing doubts about his probity.

His vice president, Dick Cheney, could be in hot water thanks to an investigation into accounting practices at oil firm Halliburton while Mr Cheney was in charge.

And Harvey Pitt, his choice to head the Securities and Exchange Commission - the main market regulator - is under fire from both Democrats and Republicans in Congress for being too close to the brokerages and companies he oversees.

Despite this, Mr Bush gave Mr Pitt his complete support.

"I support Harvey Pitt," he said, pointing out that in confirmation hearings last year every single senator had voted in favour of his appointment.

"I think that meant that they though he was the right man for the job and I still think he is."

Watchdog boost

Mr Bush said he believed the vast majority of corporate executives in the US were decent, honourable people, but a few had created the stains of recent months.

He promised to set out a plan to give more funding and more strength to the business watchdog, the Securities and Exchange Commission (SEC).

His plan is likely to be similar to that proposed by Mr Pitt himself and a bill passed by the House of Representatives in April, rather than a harsher, Democrat-backed bill debated in the Senate on Monday.

Mr Bush was also pressed on his failure to disclose share details as director of Harken Energy Corporation.

He said those who were attacking him on this issue were politically motivated.

"People are going to attack me based on Harken," he said. "That's nothing new... This is recycled stuff."

The story had been fully looked into by the SEC and "there's no case there," he added.