Malcolm Lees, 48, left a tape- recorded message in which he said: 'If I was to tell all the truth it would bring down a lot of people, important people. I don't want to do that. It is far better for me to do this.'
The Serious Crimes Squad of Cheshire Police is investigating alleged financial irregularities within BNFL.
At the beginning of March, BNFL's company secretary, Harold Bolter, resigned after it was revealed that several thousand pounds worth of redecoration work on his homes had been billed to the company. Brian Kerr, a senior manager at the company's Risley headquarters, was sacked at the beginning of April in connection with the same inquiry and is appealing against his dismissal.
The work done for Mr Bolter, a board director, had been carried out by a company which was also a contractor to BNFL. When he resigned, Mr Bolter said that he had had no knowledge of the payments and that he would reimburse the company.
The tape was found next to Mr Lees' body in a bedroom at his home in Locking Stumps, Warrington, on 4 February - the day he had been given an ultimatum to return to work. He had not yet gone back after the Christmas break.
John Hibbert, the Warrington coroner, recorded a suicide verdict on Mr Lees, who died from an overdose of anti-depressants combined with alcohol.