LONDON—BP PLC has decided to draw the curtains on its solar business after 40 years, shutting down what was once earmarked as a key division in its quest to develop greener sources of energy.

"We've tried and struggled to make money from it," a spokesman said, confirming reports of an internal email sent by Mike Petrucci, chief executive of BP Solar, that said the group was finding it difficult to sustain long-term returns for the division in the face of continued global economic uncertainty.

The move will affect around 100 staff world-wide. BP has gradually wound down its solar business over recent years in the face of greater competition from China, with its concentration having shifted increasingly from the high-volume manufacture of individual panels for consumers to fewer large-scale projects.

The company will now look to sell its remaining solar interests, the spokesman said. These include a 32-megawatt solar plant at the U.S. Department of Energy's Brookhaven National Laboratory on Long Island, New York, as well as the 150 megawatt Moree project in Australia. The spokesman cautioned that proceeds from the sales were expected to be negligible in the context of BP's wider asset-divestment program enacted to help recover some of the costs from last year's devastating rig explosion and oil spill in the Gulf of Mexico.

Western solar manufacturers have come under pressure in recent months, as cheaper Asian suppliers and a reduction in subsidies designed to encourage consumers to install the technology have conspired to dent profits. U.S. panel maker Solyndra LLC sought Chapter 11 protection in September, despite receiving hundreds of millions in government loans, while Germany's Solon SE filed for bankruptcy earlier this month.