Osram, which is grappling weakening demand in all of its divisions, said in February that the private equity groups were looking at whether to jointly bid for up to 100 percent of the German group's shares.

But the potential bidders were rattled by a trading update in March when Osram slashed its 2019 forecast and said it expects full-year revenue to decline between 11 and 14 percent, Manager Magazin reported.

"Confidence in the investment and financing case has sunk considerably," Manager Magazin quoted an investment banker involved in the deal as saying.

Osram did not immediately respond to a request for comment. Carlyle Group could not be reached for comment. Bain Capital declined to comment.

Due to the fluctuations in Osram's business, banks were expected to provide a far smaller loan package which in turn would reduce the return on investment prospects of the private equity groups when they exit, the magazine said, without citing sources.

Instead of a bid of up to 45 euros previously forecast by analysts, insiders now expect at most a small premium on the current price of about 30 euros, the magazine said.

Shares in Osram, which have shed more than 40 percent of their value over the past year, fell 6.2 percent to trade at 30.9 euros by 0747 GMT.

Osram, with a market value of around 3.2 billion euros (£2.7 billion), was once part of Siemens and mainly sells its products to car manufacturers.

(Reporting by Caroline Copley; Editing by Tassilo Hummel and Michelle Martin)