US President George W. Bush received confidential information about Harken Energy's troubles four months before he unloaded most of his shares in the Texas oil company where he served as an outside director, according to documents from the Securities and Exchange Commission.

In a February 1990 letter to directors - including Mr Bush - Mikel Faulkner, Harken's president, conceded that the previous year's profitability would be "disappointing", and warned that the failure to consummate a deal with a subsidiary had left Harken "with little cash flow flexibility".

Mr Faulkner further said the company would continue to be "severely limited in our activities due to cash restraints" unless it completed a share offering or asset sales.

The disclosure comes as Mr Bush and Vice-President Dick Cheney face mounting questions about their ties to big business amid a wave of accounting scandals.

Opinion polls reveal that Americans are increasingly questioning Mr Bush's handling of the Harken stock sale. Meanwhile, Democratic politicians have called for the SEC to re-open an investigation into the transaction.

The SEC is already probing accounting treatments of cost overruns used at Halliburton, the energy services company headed by Mr Cheney in the 1990s.

Mr Bush came under scrutiny for failing to notify the SEC in a timely manner after he sold about two-thirds of his Harken shares for $848,560 in June 1990. In August, the company reported a $23m loss that led its share price to dip.

Mr Bush has repeatedly said that the SEC concluded there was no basis for a case against him after a preliminary investigation of the matter. But this has failed to erase many doubts because the then-chairman of the SEC was appointed by Mr Bush's father, the former President George Bush.

Mr Faulkner's letter and other Harken documents were published on Friday by the Center for Public Integrity, a non-partisan watchdog group.

CPI said the materials suggested Mr Bush had some knowledge of the details of Harken's controversial sale of Aloha Petroleum. The company had to restate the deal after it was structured in a way that concealed large losses at Harken.

Nonetheless, CPI concluded that they did not "unambiguously resolve" what Mr Bush knew about the transaction and when he knew it.