The White House has given lawmakers investigating the collapse of bankrupt energy giant Enron access to thousands of pages of secret documents.

The documents detail the contact between Enron officials and the Bush administration as the scandal unfolded.

A US senate committee voted to subpoena documents on the White House's links with Enron last month.

But the White House is refusing to hand the documents over physically until an agreement is made to restrict their release to the public.

No instance of wrong doing by anyone in the White House has been found so far.

Security measures

The role of the Bush administration, which is renowned for its close links with energy firms, has come under close scrutiny since the collapse of Enron.

The subpoena came after Senator Joseph Lieberman said the White House had not responded quickly enough to requests for information.

The White House insisted the subpoena was "unnecessary", and would make the appropriate material available in due course.

It has now made documents available for inspection within the White House complex.

But it is refusing to provide copies of the documents until an agreement is made to safeguard the security and confidentiality of the documents.

Campaign contributions

Enron, one of the US' most high-profile corporate success stories of the 1990s, filed for bankruptcy protection late last year after it emerged it had hidden millions of dollars in debt using a complex series of external financial partnerships.

Enron's bankruptcy, the biggest in US corporate history, left investors nursing heavy losses and wiped out many former Enron employees' retirement savings.

The company was a major donor to President George W. Bush's 2000 presidential campaign, and was one of a small group of energy companies thought to have been behind much of the administration's energy policy.

The Bush administration, known for its ties with the energy industry, has admitted that Enron chairman Kenneth Lay made phone calls to senior government officials late last year as the company neared bankruptcy.

Fall-out

Enron's collapse sent shock waves through US financial markets, with investors dumping shares in any company using less than transparent accounting procedures.

Another strand of the multiple investigations has focused on why federal regulators did not detect the company's irregular financial practices sooner.

It has also destroyed the reputation of the global accounting giant Andersen, which had failed to spot any irregularities while auditing Enron's accounts.

Andersen's US audit partnership is currently defending itself against criminal charges stemming from the destruction of Enron-related documents by some of its executives.