LONDON—A U.K. High Court judge has refused a motion to stay contempt of court proceedings against a senior London market energy broker involved in a noncompete dispute between units of Marsh & McLennan Cos. Inc. and Aon Corp.

The broker, who in 2009 left Marsh Ltd. to join Aon Ltd., admits to throwing a laptop computer into a pond to cover up his involvement in a bid to win business that Marsh contends broke the terms of a six-month notice period, during which he was barred from working for or with a Marsh competitor.

In addition to facing those charges, Euan Nicolson, a former managing director in the construction team of Marsh's energy practice in London, is accused of making false statements and breaching court orders.

Mr. Nicolson is accused of helping Aon bid for the business of Milan-based energy company Saipem S.p.A., an account previously brokered by Marsh, during his notice period, which ran from May to October 2009.

He also is accused of breaching an Oct. 1, 2009, court order that he must not destroy, tamper with, cancel or part with possession of any equipment—including computers and memory sticks—or destroy, delete or tamper with any documents relating to the case.

In a witness statement—his third in relation to this case—Mr. Nicolson admitted that he breached that order and that he had not previously told the truth about when he had disposed of a laptop computer used to keep in touch with five former Marsh colleagues who also joined Aon, among other things.

The laptop computer, which Mr. Nicolson admitted he had thrown into a pond near his home, was recovered by a forensics company employed by Marsh, court documents show.

Mr. Nicolson also admitted disposing of computer memory sticks containing personal and Marsh-related data in a river.

In the third witness statement, Mr. Nicolson also acknowledged he had assisted Aon with other business during his notice period, though he said his involvement had been limited and was not significant.

Mr. Nicolson could face jail time if he is found guilty of the charges.

In the High Court last week, Justice Akenhead ordered a full hearing later this year on the allegations of contempt of court and making false statements.

A spokesman for Marsh declined to comment on the case. Aon said it was unable to comment on ongoing legal proceedings.

The High Court case is Marsh Services Ltd. & Marsh Ltd. and Euan David Nicolson, Alister Gavin Laird & Aon Ltd., HQ09X04381.