ROBERT MORGENTHAU, the Manhattan district attorney, is preparing to charge at least one banker from JP Morgan Chase amid allegations that trades organised by the group helped to conceal billions of dollars of debt at Enron, the bankrupt energy company.

Dozens of employees from the bank have appeared over recent months before a closed grand jury in New York to explain the trades, with dealings in gas supply contracts between Enron, JP Morgan and Mahonia, a Jersey-based company, the focus of the questions.

Sources close to the hearings told The Times last night, however, that the hearings, which have also involved staff of other Wall Street firms, are drawing to a close and that criminal charges “against a couple of JP Morgan people” are expected.

It is unlikely that Mr Morgenthau will bring charges against JP Morgan itself, or any of its senior officers, but members of the bank’s structured finance department, or its Enron client officers, are the most likely to face legal action.

A spokeswoman for Mr Morgenthau declined to comment, while JP Morgan would only say: “We are continuing to co-operate fully with the district attorney’s investigation.” The bank has admitted for the past nine months that the inquiry was ongoing, but it is understood the company is ready for an imminent announcement from Mr Morgenthau’s office.

The banker, or bankers, likely to be charged are expected to be accused of knowingly orchestrating deals and mechanisms to help Enron to conceal from investors the billions of dollars of debt that caused its downfall in December 2001.

Mahonia was a paper company set up by Chase and Company in 1992, although it was not directly owned by the bank. Chase has since become part of JP Morgan.

JP Morgan used Mahonia to provide about $1 billion (£620 million) of finance to Enron to help it to pay for gas trades. It is alleged the trades under investigation involved transferred gas from Mahonia to JP Morgan, which then sold the gas back to Enron. “Essentially they would fabricate a deal between themselves,” a source said.